ASSAFWAH PRIVATE SCHOOLS IGCSE NOTES- PHYSICS LIGHT Prepared by M.Govidara! e"ai#$ "%&ovidara!'ya(oo.)o. "%&ovidara!'ya(oo.)o.*+ *+ 1. Ligh Lightt is is a form form of ener energy gy.. 2. Light Light is a wave wave moti motion, on, rathe ratherr like like the water water wave wavess you see see on a pond. pond. 3. Light travels travels at a very high speed speed – about milli million on time time faster faster than than the speed of sound. sound. # 4. Speed Speed of ligh lightt is 3 3 mill million ion metr metres es per se!ond se!ond or or 3 " 1 m$s. Ray o, #i&( %. Light Light travel travelss in in a strai straight ght line, line, !alled !alled re)i#iear . &. Light Light is is repre represen sented ted by by a line line with with arrow arrow,, !all !alled ed ray o, #i&( .
'. #. ).
(f all all rays rays are are paral parallel lel they they are are !all !alled ed parall parallel el rays rays.. (f all all rays rays are are !onverg !onverging ing to to a point, they are are !alled !alled !onverging !onverging rays (f all all rays rays are are divergi diverging ng to a point, point, they they are are !alled !alled diverg diverging ing rays. rays.
5arallel rays
1. 11. 11. 12. 13. 14. 1%. 1&. 1'. 1#. 1). 2.
7iverging rays 6onverging rays *b+e!t *b+e!t that that produ!es produ!es their their own visib visible le light light is !alled !alled #*"io* o*r)e – e" the Sun, other stars, lamps, televisions et!. *b+e!t *b+e!tss that that are illumi illuminat nated ed by light light from other other sour!e sour!ess and refle!t refle!ted ed it into our eyes, eyes, !alled o #*"io* ob+e!ts – e" the moon, paper, walls, stone and most of ob+e!ts. Trapare Ob!e) . he ob+e!ts in whi!h light passes through it is !alled transparent ob+e!t. -" – lass, pure water et!. Opa/*e Ob!e) / he ob+e!t in whi!h light !an not pass through is !alled *pa0ue ob+e!t. -" – ood, !ard board, stone, wall, metal, et!. Tra#*)e Tr a#*)e Ob!e) / he ob+e!t in whi!h light passes partially is !alled translu!ent ob+e!t -" – water, paper, sun glass et!. !o ntinue to travel in straight lines, S(ado0 / Shadows are formed when some rays of light !ontinue whi!h other rays are stopped by an ob+e!t. -!lipse -!lipse is good e"ample e"ample for shadow. shadow. e !an see an ob+e!t ob+e!t only if light light from it enters enters our eyes. eyes. REFLECTION OF LIGHT / he pro!ess pro!ess of returning returning light light ba!k to same medium medium is !alled !alled refle!tion. refle!tion. he refle!tion is two types 1. egular refle!tion refle!tion 2. (rregular refle!tiondiffused refle!tiondiffused refle!tion
egular efle!tion
(rregular efle!tion
21. he regular regular refle! refle!ti tion on refle! refle!ts ts parall parallel el rays rays of light light as parall parallel el rays, rays, while while irregul irregular ar refle!tion refle!ts parallel light rays into different dire!tions, as shown in figure. 22. egular egular refle!t refle!tion ion is from from regula regularr smooth smooth surfa!e, surfa!e, while irregula irregularr refle! refle!tio tion n is from from irregular surfa!e. 23. he ray whi!h whi!h in!ident in!ident on a surfa!e surfa!e is !alled !alled i)ide ray . 24. he ray whi!h whi!h refle refle!te !ted d from a medium medium is !alled !alled re,#e)ed ray . 8n imaginary line drawn perpendi!ular to the mirror at the point where the in!ident ray strikes it is !alled the or"a#. 2%. he a&#e o, i)ide)e is the angle between in!ident ray and normal. 2&. 2&. Simi Simila larl rly y a&#e o, re,#e)io is angle between refle!ted ray and normal. =ormal
(n!iden!e ray 8ngle of in!iden!e
i
r
efle!ted ray 8ngle of efle!tion
he thing thing whi!h pla!ed pla!ed in front front of a mirror mirror is !alled !alled Ob!e) . he thing thing whi!h is seen$formed seen$formed in the the mirror mirror is !alled !alled I"a&e. ypes ypes of (mages (mages / he he images are are two types types a rea# image 9 b vir*a# image. Rea# i"a&e is the one whi!h !an be fo!used on a s!reen. -" 6inema image. Vir*a# i"a&e is the one whi!h !an not be fo!used on the s!reen. -" (mage seen in plane mirror. 32. efle!tion efle!tion does does not !hanges !hanges speed speed 9 wavelength wavelength of the light. light. 33. he image image from a plane plane mirror mirror !an not be be fo!used on on a s!reen. s!reen. 34. LAWS OF REFLECTION$ 1. he angle of in!iden!e e0uals the angle of refle!tion. i = r 2. he in!ident ray, the refle!ted ray and the normal all lie in the same plane. 3%. Na*re o, I"a&e ,or"ed by p#ae "irror . a. Si:e Si:e of image image forme formed d by mirro mirrorr is same same as ob+e! ob+e!t. t. b. ;irtual ;irtual image !. -re!t image d. Late Latera rall lly y inver inverte ted d e. 7istan!e 7istan!e of image from the mirro mirrorr is same same as as that of ob+e!t. ob+e!t. 3&. (f we pla!e an ob+e!t ob+e!t 3!m away in front front of a mirror mirror,, then the image image formed formed is 3!m behind the mirror. he figure above shows how the refle!ted rays appear to !ome from the image. hus the line +oining the ob+e!t to the image is at right angles to the mirror. he image in the plane mirror is laterally inverted. 3'. 6omplete 6omplete the ray diagram diagram and lo!ate lo!ate the position position of image image
21. he regular regular refle! refle!ti tion on refle! refle!ts ts parall parallel el rays rays of light light as parall parallel el rays, rays, while while irregul irregular ar refle!tion refle!ts parallel light rays into different dire!tions, as shown in figure. 22. egular egular refle!t refle!tion ion is from from regula regularr smooth smooth surfa!e, surfa!e, while irregula irregularr refle! refle!tio tion n is from from irregular surfa!e. 23. he ray whi!h whi!h in!ident in!ident on a surfa!e surfa!e is !alled !alled i)ide ray . 24. he ray whi!h whi!h refle refle!te !ted d from a medium medium is !alled !alled re,#e)ed ray . 8n imaginary line drawn perpendi!ular to the mirror at the point where the in!ident ray strikes it is !alled the or"a#. 2%. he a&#e o, i)ide)e is the angle between in!ident ray and normal. 2&. 2&. Simi Simila larl rly y a&#e o, re,#e)io is angle between refle!ted ray and normal. =ormal
(n!iden!e ray 8ngle of in!iden!e
i
r
efle!ted ray 8ngle of efle!tion
he thing thing whi!h pla!ed pla!ed in front front of a mirror mirror is !alled !alled Ob!e) . he thing thing whi!h is seen$formed seen$formed in the the mirror mirror is !alled !alled I"a&e. ypes ypes of (mages (mages / he he images are are two types types a rea# image 9 b vir*a# image. Rea# i"a&e is the one whi!h !an be fo!used on a s!reen. -" 6inema image. Vir*a# i"a&e is the one whi!h !an not be fo!used on the s!reen. -" (mage seen in plane mirror. 32. efle!tion efle!tion does does not !hanges !hanges speed speed 9 wavelength wavelength of the light. light. 33. he image image from a plane plane mirror mirror !an not be be fo!used on on a s!reen. s!reen. 34. LAWS OF REFLECTION$ 1. he angle of in!iden!e e0uals the angle of refle!tion. i = r 2. he in!ident ray, the refle!ted ray and the normal all lie in the same plane. 3%. Na*re o, I"a&e ,or"ed by p#ae "irror . a. Si:e Si:e of image image forme formed d by mirro mirrorr is same same as ob+e! ob+e!t. t. b. ;irtual ;irtual image !. -re!t image d. Late Latera rall lly y inver inverte ted d e. 7istan!e 7istan!e of image from the mirro mirrorr is same same as as that of ob+e!t. ob+e!t. 3&. (f we pla!e an ob+e!t ob+e!t 3!m away in front front of a mirror mirror,, then the image image formed formed is 3!m behind the mirror. he figure above shows how the refle!ted rays appear to !ome from the image. hus the line +oining the ob+e!t to the image is at right angles to the mirror. he image in the plane mirror is laterally inverted. 3'. 6omplete 6omplete the ray diagram diagram and lo!ate lo!ate the position position of image image
*
*
3#. 5eris!ope 5eris!ope / 5eris!ope 5eris!ope is an opti!al opti!al instrument instrument used in submarines submarines 9 tanks so that that people below the surfa!e !an see what is happening above the surfa!e.
3). REFRACTION efra! a!ti tion on of is the the pro! pro!es esss of light light trav travel el from from one REFRACTION OF LIGHT/ efr medium into other with !hange of its properties. 4. 8lthoug 8lthough h light light travels travels in strai straight ght lines lines in one transp transpare arent nt material material,, su!h su!h as in air, air, if it passes into a different material, su!h as water, it !hanges dire!tion at the boundary between the two. he bending of light when it passes from one medium to other is !alled ->86(*=.
i
air
glass 8ngle of refra!tion r
i 8. 8 ray ray of of ligh lightt is be o0ard the normal when it enters from less denser medium into an opti!ally denser medium at an angle from air to glass
?. 8 ra ray is i s be a0ay from from the the norm normal al when when it enter enterss an opti! opti!al ally ly less less dens densee mediumfrom glass to air 6. 8 ray emerg emerging ing from a parallel parallel sided sided blo!k is parallel parallel to the ray entering entering , but is displa!ed sideways 7. 8 ray ray traveling traveling along along the normal normal is not refra!t refra!ted. ed. 41. La0 o, Re,ra)io / 1. he in!ident ray, refra!ted ray, ray, normal and emergent ray are all lie in same plane. 2. he atio of sine angle of in!iden!e and sine angle of refra!tion is a !onstant, !alled refra!tive inde". his law is !alled Se##1 La0. (t is also !alled as ie #a0. Sin i
efra!tive inde" of a substan!e n @ efra!tive inde" of a substan!e n @
Sin r Speed of light in vacuum $ air Speed of light in the subs tan ce
42. hen light under under goes refra!tio refra!tion, n, the speed of light in denser medium medium is less than than that in less denser medium.
4'. hen hen light light passes passes at small small angles angles of in!ide in!iden!e n!e from an opti!ally opti!ally dense dense to a less less dense medium i.e from glass to air, there is a strong refle!ted ray and a weak ray refle!ted ba!k into the denser medium. 8s shown in figure 1. 4#. (n!reasing (n!reasing the angle angle of in!iden!e at denser medium medium in!reases in!reases the angle of refle!tio refle!tionray nray 1 in figure. figure. 8t a !ertai !ertain n angle angle of in!iden!e in!iden!e,, !alled !alled the )rii)a# a&#e A!B, the angle of refra!tion is ) .ray 2. >or angles of in!iden!e greater than A!Bray 3, the refra!ted ray disappears and all the in!ident light is refle!ted inside the denser medium .like in figure. he light does not !ross the boundary bou ndary and is said to undergo Toa# Iera# Re,#e)io . r
air
1 water
i 2
6 3
C6
4). Codiio ,or Toa# Iera# Re,#e)io / 1. Light should travel from denser to less denser medium 2. 8ngle of in!iden!e at denser medium should be greater than !riti!al angle. %. 8t !riti!al angle r @ ) i @ 6 sin
efra!tive inde" n @
r
sin i
sin ) =
sin C
1 =
sin C
∴n @
1 sin
C
%1. App#i)aio o, Toa# Iera# Re,#e)io 1. *pti!al illusion 2.
otal (nternal efle!tion through prism
? ?
8
8 ?
Light through opti! fibre
LENSES %4. Lenses are spheri!al surfa!es. here are 2 types of lenses. a. 8 lens whi!h is thi!ker at the !enter than at the edges is !alled a )ove3 #e. he rays obtained after a !onve" lens are !onverging so we say it as a )over&i& #e as shown in the figure below. b. he lens whi!h is thinner at the !enter is !alled a )o)ave lens. he ray obtained after refra!tion through !on!ave lens is diverging so we say it as a diver&i& #e .
6onve" or 6onverging lens
6on!ave or diverging lens
5lano !onve"
5lano !on!ave
%%. Ter" i Lee / 4. Opi) )ere o, a #e5O6 / he geometri! !entre of a lens is !alled opti! !entre.
7. Cere o, )*rva*re5C or 7F6 / he !entre of sphere in whi!h the lens is a partobtained by e"tending the lens is !alled !entre of !urvature. 8. Radi* o, )*rva*re 5R6 / he radius of the sphere in whi!h the lens is a part. 9. Pri)ip#e Fo)* 5F6 / 8 point in whi!h all parallel light rays !onverge after refra!tion through lensor appears to be starting from it for !an!ave lens. his is also !alled as fo!us :. Pri)ip#e A3i / 8n imaginary light rays passing through !entre of !urvature and prin!iple fo!us is !alled prin!iple a"is. ;. Fo)a# #e&( 5,6 / he distan!e between opti! !entre and prin!iple fo!us is !alled fo!al length. (t is represented as f.
6onve" lens > 5rin!iple a"is 2>
*
>
>
6 or 2>
%&. R*#e o dra0 ray dia&ra" 1. 8ny ray parallel to prin!iple a"is after refra!tion it will pass through fo!us. 2>
>
>
ule 1
2>
>
2>
>
>
ule 2 >
ule 3 2. 8ny ray passing through prin!iple a"is after refra!tion if will pass parallel to prin!iple a"is. 3. 8ny ray passing through opti! !entre after refra!tion it will go in same straight line without !hange in dire!tion. %'. IMAGE FORME< =Y CONVE> LENS Poiio o, ob!e)
1. 8t infinity
Ray
Na*re o, (e i"a&e
(mage is at > eal 7iminished (nverted
ays are parallel to prin!iple a"is
2>
5rin!iple a"is
>
>
(mage
ays are not parallel to prin!iple a"is
2>
5rin!iple a"is
>
>
(mage
2. ?eyond 6 or 2>
2>
>
>
2>
5rin!iple a"is
(mage is between> 9 2> eal 7iminished (nverted
(mage
(mage is at 2> eal Same si:e
3. 8t 2> 2>
>
>
2>
5rin!iple a"is
(mage
4.?etween 2> 9 > >
>
2>
5rin!iple a"is
2>
(mage beyond 2> eal -nlarged (nverted
is
(mage *b+e!t is not point sour!e
%. 8t > 2>
>
5rin!iple a"is >
2>
*b+e!t is point sour!e
(mage is at infinity. =ature is unpredi!table
*b+e!t is point sour!e
2>
>
2>
>
5rin!iple a"is
&.?etween >9* 2>
>
>
5rin!iple a"is
2>
(mage
(mage is on same side of ob+e!t ;irtual -nlarged -re!t
%#. (n a 6*=68;- lens parallel rays are diverged so that they appear to !ome from the prin!ipal fo!us > of the !on!ave lens 59. A FAT LENS S A ST!"N# LENS $ %T& A S&"!T F"CAL LEN#T&. '(. A T&N LENS S A %EA) LENS$ %T& A L"N# F"CAL LEN#T&. &eight $ si.e of (m age 3hi 4 ,is tan ce of image( - ) &1. MAGNIFICATION / m @ &eight $ si.e of "b+ect 3ho 4 ,is tan ce of ob+ect (* ) =
" ?
hi
=
ho
- *
1
&2. Po0er o, Le / 5 @ Focal length in metre &3. Dnit of power is 7iopter7, 1 7 @ 1mE1
=
1
f
&4. @e o, Le 6onve" lenses are generally used to enlarge small or mi!ros!opi! ob+e!ts 1. Lens is used in all 5ro+e!tors, 6ameras, of the lens. he image is seen on same side of the ob+e!t. he nature of the image is virtual, ere!t and magnified.
>
>
2>
5rin!iple a"is
2>
(mage
&&. Pi (o#e )a"era . (t a simple devi!e to demonstrate the nature of image formed by a lens. his !onsists of a !artoon bo" !ontains small hole in it. 8 !andle lighted !andle pla!ed in front of the hole produ!es small, inverted and real image on other side the bo", whi!h !an be seen from the top of the bo". he hole a!ts as lens in the !amera. (f the ob+e!t is !loser and !loser, the image is bigger and bigger. Similarly, if it far away the si:e is smaller. he magnifi!ation is given by &eight $ si.e of (m age 3hi 4 ,is tan ce of image( - ) m@ &eight $ si.e of "b+ect 3ho 4 ,is tan ce of ob+ect ( * ) =
(mage distan!e
*b+e!t distan!e
&'. Ca"era. 8 !amera !onsists of a lightEtight bo" with a !onve" lens at one end and the film at the other end. he parallel light rays from an ob+e!t pass through the lens and !onverge at the film. he nature of the image formed is real, inverted and diminished.
>ilm
2>
>
>
2>
5rin!iple a"is
(mage
6amera
&#.
the refra!tive inde" of glass is different for ea!h !olor. he refra!tive inde" is greatest for violet light and least for red light. &). he !olors in order are ed, *range, Gellow, reen, ?lue, (ndigo, ;iolet.*G . . ;(?. ed at the top and violet at the bottom. he !olor that is deviated bent least by the prism is red, violet is deviated through a larges angle as shown in the diagram. 7ispersion of white light into its seven !olours represent that the white is !omposition of seven !olours. '. Ne0o1 Co#o*r 0(ee# / hite !olour !onsists of seven !olours, then we should be able to get all seven !olours by rotating the wheel 0ui!kly so that the !olour appears to '1. F* 7*-S 8 5(S< 7(S5-S- F(- L(F (=* 8 S5-6D
hite light
8ngle of deviation
; E>ERCISES
1. he angle between an in!ident ray and the mirror is 3. a. hat is the angle of in!iden!eH b. hat is the angle of refle!tionH !. hat is the total angle turned by the rayH 2. 8 boy with a mouth %!m wide stands 2m from a plane mirror. here is his image and how wide is the image of his mouthH Fe walks towards the mirror at 1m$s. 8t what speed does his image approa!h himH 3. >ind the known angles
=ame the following
4. 6omplete the ray diagram
Single hite light 6olour light %. >rom the pi!ture answer the following 0uestion a. 8t what distan!e he !an see his image H IIIIIIIIIIIIIIIIIIIIIIII b.6an he see his foot IIIIIIIIIIIIIIIIIIIIIIII !. (f he is 1% !m tall, what minimum height of mirror is re0uired to see he image he wants to see his foot what distan!e he has to move from the mirrorH 2!m
&. 6opy and !omplete the diagram
42
E>ERCISES 1. hi!h diagram !orre!tly shows a ray of light passing through a re!tangular glass blo!kH
2. hi!h diagram !orre!tly shows rays passing through a !amera lensH
3. 8 ray of light passes from glass into air at an angle of in!iden!e of 4 o. he glass has a
!riti!al angle of 42. hi!h diagram shows what happens to the rayH
4. ays of light enter and leave a bo".
hat !ould be inside the bo" to make the rays behave as shownH 8 a !onverging lens ? a parallelEsided glass blo!k 6 a plane mirror 7 a triangular prism
5. 8 thin !onverging lens is used to produ!e, on a s!reen, a fo!used image of a !andle.
he s!reen and the lens are moved ba!k and forth and various fo!used images are produ!ed on the s!reen. hi!h statement is always trueH 8 he image is at the prin!ipal fo!us fo!al point of the lens. ? he image is bigger than the ob+e!t. 6 he image is !loser to the lens than the ob+e!t is. 7 he image is inverted.
6. he image of a !lo!k fa!e as seen in a plane mirror is shown.
hat is the a!tual time on the !lo!kH A 1.2% = 1.3% C 1.2%
< 1.3%
7. hree rays of light fall on a !onverging lens as shown lens
hi!h diagram shows the path of the rays after passing through the lensH
8. he diagram shows the image of a !lo!k in a plane mirror. hat time is shownH
8 2/2% ? 2/3% 6 )/2% 7 )/3% 9. 8 ray of light passes through a window. hi!h path does it takeH
10. Astudent looks at the letter 5 on a pie!e of paper, and at its refle!tion in a mirror.
hat does he seeH
11. he !riti!al angle for a glass $ air boundary is 6.
hi!h diagram shows the !orre!t path of the light rayH
12. he diagram shows the image of a !lo!k fa!e in a plane mirror.
hi!h of these times is shownH 8 2.2% ? 2.3%
6 ).2%
7 ).3%
13. he ray diagram shows how an image is formed by a !onverging lens.
hat is the fo!al length of this lensH 8 # !m ? 1 !m 6 1# !m
7 24 !m
14. he ray diagram in >ig. 11.1 shows a lens forming an image ((J of an ob+e!t **J.
5a6 State 5i6 whi!h of the marked points is a prin!ipal fo!us of the lens, .......................................
5ii6 whi!h distan!e is the fo!al length of the lens............................................................. 5b6 hi!h of the following words des!ribe the imageH i!k all that are !orre!t. real virtual inverted upright enlarged diminished 5)6 *n >ig. 11.1, draw one other ray that goes from *J, the top of the ob+e!t, to the image. 15. 5a6 8 man looks at his refle!tion in a verti!al mirror. his is shown from the side in >ig. 1
5i6 *n >ig.1, a!!urately mark with a )#ear do labelled = where the image of the tip A of the manBs beard will be. 5ii6 *n >ig.1, a!!urately draw a ray from the tip of the manBs beard that refle!ts from the mirror and goes into his eye. Gou may use faint !onstru!tion lines if you wish. Dse arrows to show the dire!tion of the ray. 5iii6 he man !an see the image, but it !annot be formed on a s!reen. hat name is given to this type of imageH ..................................................................................................................................
Fi& 4
Fi& 7 efle!tion seen in the mirror
5iv6 rite down the e0uation that links the angles of in!iden!e and refle!tion that the ray makes with the mirror. 5b6 8 girl looks into a bathroom mirror to brush her hair. >ig.2 shows what she sees in the mirror. 5i6 (n whi!h hand is she holding the brushH i!k one bo". left hand K right hand K
5ii6 She has a spot on her skin +ust below her left eye. ig. 12.2 where this will appear on the refle!tion. 16. 5a6 he filament of a lamp is pla!ed at the prin!ipal fo!us of a lens, as shown in >ig.1.
Fi&. 4 *n >ig.1, !ontinue the three rays through the lens and out into the air on the right of the lens. 5b6 he lens in >ig. '.2 has a fo!al length of 2. !m.
*n >ig. '.2, 5i6 mark and label the positions of the prin!ipal fo!us on the left of the lens and the prin!ipal fo!us on the right of the lens, 5ii6 !arefully draw a ray from the top of the ob+e!t, parallel to the a"is, through the lens and !ontinue it until it rea!hes the edge of the s0uared area.
Fi&. 7 5iii6 !arefully draw a ray from the top of the ob+e!t, whi!h travels parallel to the a" is a,er it has passed through the lens. 5iv6 draw and label the image. 17. >ig. &.1 shows an opti!al fibre. G is a ray of light passing along the fibre.
5a6 *n >ig. &.1, !ontinue the ray G until it passes M. N1O 5b6 -"plain why the ray does o leave the fibre at G. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ 5)6 he light in the opti!al fibre has a wavelength of 3.2 " 1 –' m and is travelling at a speed of 1.) " 1#m$s. 5i6 6al!ulate the fre0uen!y of the light.
fre0uen!y @ PPPPPPP... 5ii6 he speed of light in air is 3. " 1#m$s. 6al!ulate the refra!tive inde" of the material from whi!h the fibre is made.
refra!tive inde" @ PPPPPPP... 18. 8 single ray of white light from the lightning is in!ident on a prism as shown in >ig.
6omplete the path of the ray to show how a spe!trum is formed on the s!reen. Label the !olours.
19. 5a6 >ig. '.1 shows a ray of blue light shining onto a glass prism. ith the aid of a straight
edge, draw a possible path of the ray through the prism and into the air until it rea!hes the s!reen.
5b6 hen a ray of white light passes through the prism, it spreads into a spe!trum of !olours that !an be seen on the s!reen. 5i6 hat is the name of this spreading effe!tH i!k one bo". 6onvergen!e K 7iffra!tion K 7ispersion K refle!tion K 5ii6 hi!h !olour is deviated least by the prismH ..................................................... 5iii6 hi!h !olour is deviated most by the prismH ................................................... s!reen 20. >ig. &.1 shows white light in!ident at 5 on a glass prism. *nly the refra!ted red ray 5Q is shown in the prism. 5a6 *n >ig. &.1, draw rays to !omplete the path of the red ray and the whole path of the violet ray up to the point where they hit the s!reen. Label the violet ray. 5b6 he angle of in!iden!e of the white light is in!reased to 4R. he refra!tive inde" of the glass for the red light is 1.%2.
6al!ulate the angle of refra!tion at 5 for the red light. angle of refra!tion @ ........................
5)6 State the appro"imate speed of 5i6 the white light in!ident at 5,
speed @ ........................
5ii6 the red light after it leaves the prism at Q.
speed @ ........................ 21. (n this 0uestion, drawing should be done !arefully. >ig. shows a ray of light striking
mirror 1 at point .
5a6 *n >ig, 5i6 draw the normal at , 5ii6 draw the ray refle!ted from mirror 1, 5iii6 mark the angle of in!iden!e using the letter i and the angle of refle!tion using the letter r . 5b6
22. 5a6 >ig. '.1 shows two rays of light from a point * on an ob+e!t. hese rays are in!ident
on a plane mirror.
Fig. 1 5i6 *n >ig.1, !ontinue the paths of the two rays after they rea!h the mirror. Fen!e lo!ate the image of the ob+e!t *. Label the image (.
5ii6 7es!ribe the nature of the image (. ............................................................................................................................................ ............................................................................................................................................ 5b6 >ig.2 is drawn to s!ale. (t shows an ob+e!t 5Q and a !onve" lens.
>ig 2 5i6 *n >ig.2, draw two rays from the top of the ob+e!t 5 that pass through the lens. Dse these rays to lo!ate the top of the image. Label this point . 5ii6 *n >ig.2, draw an eye symbol to show the position from whi!h the image should be viewed. 23. >ig. shows a ray of light *5Q passing through a semiE!ir!ular glass blo!k.
5a6 -"plain why there is no !hange in the dire!tion of the ray at 5. ......................................................................................................................................... ........................................................................................................................................ 5b6 State the !hanges, if any, that o!!ur to the speed, wavelength and fre0uen!y of the light as it enters the glass blo!k. ......................................................................................................................................... ......................................................................................................................................... ........................................................................................................................................
5)6 8t Q some of the light in ray *5Q is refle!ted and some is refra!ted. *n >ig, draw in the appro"imate positions of the refle!ted ray and the refra!ted ra y. Label these rays. 5d6 he refra!tive inde" for light passing from glass to air is .&'. 6al!ulate the angle of refra!tion of the ray that is refra!ted at Q into air.
angle @ PPPPPP. 24. 8n inventor is trying to make a devi!e to enable him to see ob+e!ts behind him. Fe !uts a
s0uare bo" in half diagonally and sti!ks two plane mirrors on the inside of the bo". 8 side view of the arrangement is shown in >ig. 1
>ig 1
>ig 2
>ig. 2 shows the arrangement, drawn larger. >ig. 2 shows parallel rays from two different points on a distant ob+e!t behind the man. 5a6 6arefully !ontinue the two rays until they rea!h the pla!e where the inventorBs head will be. 5b6 Look at what has happened to the two rays. hat !an be said about the image the inventor seesH ................................................................................................................................................ 25. 5a6 8 beam of light is travelling parallel to the a"is of a thin lens, as shown in >ig.1 8fter
passing through the lens, the rays all pass through the point >.
>ig 1 5i6 hi!h word best des!ribes what happens to the raysH i!k one bo". he rays !onverge K 7iffra!t K 7isperse K efle!t K 5ii6 *n >ig. 12.1, !omplete the paths of the two rays. 5iii6 6omplete the following senten!e, referring to >ig. 1. he fo!al length of the lens is the distan!e between point .............. and point ..............T 5b6 (n this part of the 0uestion, you are re0uired to draw an a!!urate ray diagram on >ig 2 for the lens in part 5a6. 5i6 >rom the top of the ob+e!t, draw a ray that, after leaving the lens, passes through >. 5ii6 >rom the top of the ob+e!t, draw a ray that passes through 5. 5iii6 rom your diagram, state two things that are the same or appro"imately the same about the image and the ob+e!t.
1. ................................................................................................................................................. 2. ................................................................................................................................................. 5v6 >rom your diagram, state one thing that is definitely different about the image and the ob+e!t. .....................................................................................................................................................
>ig 2 26. 5a6 >ig.1 shows the results of an e"periment to find the !riti!al angle for light in a
semi!ir!ular glass blo!k. >ig.1
>ig 1 he ray of light 5* hits the glass at * at an angle of in!iden!e of R. Q is the !entre of the straight side of the blo!k. 5i6 ig.1. 6riti!al angle @ ......................... 5ii6 -"plain what is meant by the critical angle of the light in the glass. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ 5b6 >ig. &.2 shows another ray passing through the same blo!k. he speed of the light between and Q is 3. U 1#m$s. he speed of the light between Q and G is 2. U 1#m$s. 5i6 State the speed of the light between G and M. speed @ ............................
5ii6 rite down an e"pression, in terms of the speeds of the light, that may be used to find the refra!tive inde" of the glass. 7etermine the value of the refra!tive inde".
refra!tive inde" @ ......................
>ig 2 5iii6 -"plain why there is no !hange of dire!tion of ray QG as it passes out of the g lass. ................................................................................................................................................ 5iv6 hat happens to the wavelength of the light as it passes out of the glassH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27. he (6S- !lass !arries out an e"periment using a !onve" lens, an illuminated ob+e!t and
a s!reen. >ig. 4.1 shows the apparatus. 8 sharp image is obtained on the s!reen. Fi&. 4
Fi& 4 5a6 5i6 Dse your rule to measure, on >ig. 4.1, the distan!e / from the illuminated ob+e!t to the !entre of the lens. / @ ............................ 5ii6 Dse your rule to measure, on >ig. 4.1, the distan!e 0 from the !entre of the lens to the s!reen. 0 @ ............................ 5iii6 >ig. 4.1 shows the apparatus drawn to 1$%th of a!tual si:e. 6al!ulate the a!tual distan!e u between the ob+e!t and the lens, and the a!tual distan!e v between the lens and the s!reen.
u @ ............... v @ ............
5iv6 6al!ulate the magnifi!ation m using the e0uation m @
- . *
m @ .......................... 5b6 he illuminated ob+e!t is triangular in shape, as shown in Fi&.7
7raw a diagram of the image as it would appear on the s!reen. 5)6 State two pre!autions that the (6S- !lass should take to obtain e"perimental readings that are as a!!urate as possible. 1. ................................................................................................................................................... ....................................................................................................................................................... 2. ................................................................................................................................................... ....................................................................................................................................................... 28. 5a6 8 narrow beam of red light strikes one fa!e of a triangular prism at 8, as shown in
>ig.1.
>ig 1 5i6 *n >ig.1, show the path of the beam until it rea!hes the s!reen. 5ii6 hat name do we use to des!ribe what happens to the beam at 8H ................................................................................................................................................
>ig 2
5b6 he red light is repla!ed by a narrow beam of mi"ed red and violet light, as shown in >ig.2. 6omplete >ig. 2 to show what happens to the red and the violet light. 5)6 he beam of red and violet light is repla!ed by a narrow beam of white light from the Sun. State what is now seen on the s!reen. ............................................................................................................................................... 5d6 he rays from the Sun also in!lude infraEred rays. (nfraEred radiation !an pass through glass. 5i6 *n >ig. 2, mark with the letter the pla!e where infraEred radiation from the Sun might strike the s!reen after passing through the prism. 5ii6 hy !an infraEred not be seen on the s!reenH ................................................................................................................................................ 5iii6 hat !ould be used to dete!t the infraEred radiationH ................................................................................................................................................ 29. >ig. shows white light in!ident at 5 on a glass prism. *nly the refra!ted red ray 5Q is
shown in the prism.
5a6 *n >ig. draw rays to !omplete the path of the red ray and the whole path of the violet ray up to the point where they hit the s!reen. Label the violet ray. 5b6 he angle of in!iden!e of the white light is in!reased to 4R. he refra!tive inde" of the glass for the red light is 1.%2. 6al!ulate the angle of refra!tion at 5 for the red light.
angle of refra!tion @ ........................ 5)6 State the appro"imate speed of 5i6 the white light in!ident at 5, speed @ ........................ 5ii6 the red light after it leaves the prism at Q. speed @ ........................ 30. 8 student investigates the refra!tion of light through a transparent blo!k. Fe pla!e the
transparent blo!k on a sheet of plain paper, largest fa!e down, and draws a line round the blo!k. Fe draws a line to represent an in!ident ray and pla!es two pins W and > in the line. >ig. %.1 shows the outline of the blo!k and the in!ident ray. 5a6 *n >ig. %.1, draw a normal to line A= at the point where the in!ident ray meets the blo!k. he in!ident ray is drawn on the diagram. he positions of the two pins W and > that mark the in!ident ray are shown. 5b6
5)6 7raw in the refra!ted ray with an angle of refra!tion of 2R. 6ontinue this line until it meets the line C<. 5d6 he ray emerges from the blo!k in a dire!tion that is parallel to the in!ident ray. 7raw in this emergent ray. 5e6 wo pins Y and are pla!ed so that the pins W and >, viewed through the blo!k, and the pins Y and all appear e"a!tly in line with ea!h other.
6arry out the following instru!tions, referring to >igs.1, 2 and 3.
Fi& 4
5a6 5la!e the transparent blo!k with its largest fa!e down on one of the ray tra!e sheets as shown in >ig. 4.1. *ne of the longest sides is to be along line PB. 5b6 7raw round the blo!k and label the !orners A, =, C and <. emove the blo!k. 5)6 5la!e the ray tra!e sheet on the pin board and push a pin > into the paper on line EF !lose to line A=. 5ush another pin W into line EF some distan!e away from line A=. 5d6 epla!e the blo!k on the ray tra!e sheet. 5e6 ;iew the images of pins W and > through the blo!k. 5la!e two pins Y and between your eye and the blo!k so that Y, and the images of W and > appear e"a!tly one behind the other. 5,6 Label the positions of pins W, >, Y and on the ray tra!e sheet. emove the pins and the blo!k. Dsing a rule, draw a line +oining and Y and !ontinue the line to meet the line C< at a point, whi!h you should label G. 5&6 7raw a line to +oin the points F and G. 5(6
Fi& 7 5la!e the blo!k on the se!ond ray tra!e sheet so that one of its longest sides is along line PB but with the largest fa!e verti!al as shown in >ig.2. Label the !orners A, =, C and <. 5!6 epeat steps 5b6 – 5(6. 5+6 5la!e the blo!k on the third ray tra!e sheet with the largest fa!e down so that one of its shorter sides is along the line PB. *ne !orner should be about 1 !m to the left of point F, as shown in >ig.3. Label the !orners A, = C and <.
>ig 3
5#6 epeat steps 5b6 – 5(6. 5"6 ithin the limits of e"perimental error, what do you !on!lude about the effe!t on the angle of refra!tion r of in!reasing the length of the ray within the blo!kH 32. n
this e/periment 0ou are to investigate the refraction of light through a transparent bloc2. e!ord all your observations and !arry out the following instru!tions referring to >ig 1.
5a6 5la!e the transparent blo!k, largest fa!e down, on the sheet of plain paper supplied. he blo!k should be appro"imately in the middle of the paper. 7raw the outline 8?67 of the blo!k . 5b6 emove the blo!k and draw the normal ==B to side 8? so that the normal is 2. !m from 8. Label the point where ==B !rosses 76. 5)6 7raw the line -> at an angle of 3R to the normal, as shown in >ig. 5d6 5la!e the paper on the pin board. 5e6 5la!e two pins 51 and 52 on line -> as shown in >ig. 5,6 epla!e the blo!k and observe the images of 51and 52 through side 67 of the blo!k so that the images of 51 and 52 appear one behind the other. 5la!e two pins 53 and 54 between your eye and the blo!k so that 5 3 and 54 and the images of 5 1 and 52, seen through the blo!k, appear one behind the other. . 5!6 . 5+6 -"tend the straight line -> within the outline of the blo!k to a point (. he distan!e >( must be e"a!tly e0ual to b. 5#6 >rom ( draw a line that meets ==B at a right angle. Label this position W. 5"6 ig. 4.1. 5a6 5osition the sheet of paper so that the hole is at the top rightEhand !orner. 5la!e the transparent blo!k on the paper with its largest fa!e down and appro"imately in the !entre of the paper. 7raw round the blo!k and label the !orners 8, ?, 6 and 7 see >ig. 1. emove the blo!k. 5b6 7raw a normal to line 8?, appro"imately at the !entre, and label the normal ==J. 5)6 7raw a line -> above the line 8? and at 3R from the normal.
>ig. 1 5e6 epla!e the blo!k on the paper. 5,6 ;iew the images of pins and through the blo!k. 5la!e two pins G and M between your eye and the blo!k so that G, M and the images of and appear e"a!tly one behind the other. 5&6 and . 5i6 and the normal. 5!6 -"tend the line -> through line 67 and to almost the edge of the paper. Label the point at whi!h the line !uts 67 with the letter F. 5+6 F. Label the points at whi!h it !uts these lines with the letters W and X.
34. (n this e"periment, you are to determine a 0uantity !alled the refra!tive inde" of the
material of a transparent blo!k. 6arry out the following instru!tions referring to >ig.
5a6 7raw a line on the sheet of plain paper parallel to and 3 mm from one of the longer edges. Label this line A=. 5b6 5la!e the transparent blo!k, largest fa!e down, on the paper with one of the shorter sides, EH, along the line A= and su!h that the distan!es EA and H= are appro"imately e0ual. 7raw the outline of the blo!k EFGH. 5)6 emove the blo!k and draw the normal NN I to side EF so that the normal !uts EF at a point T, 4 mm from E. 6ontinue the normal so that it !uts the line HG at a point W. Label this point. 5d6
5,6 5la!e two pins P4 and P7 on line VT, as shown in >ig. 5&6 epla!e the blo!k and observe the images of P4 and P7 through side GH of the blo!k so that the images of P4 and P7 appear one behind the other. 5la!e two pins P8 and P9 between your eye and the blo!k so that P8 and P9 and the images of P4 and P7, ee (ro*&( (e b#o)+ appear one behind the other. . 5i6 7raw the line >T. 5!6 @ c and >T @ d . 5+6 6al!ulate n, the refra!tive inde" of the material of the blo!k, using the e0uation below.
n@
a × d b×c
5#6 State and e"plain the reason for oe pre!aution that you took to gain an a!!urate result. 35. >ig. shows the outline of a transparent perspe" blo!k used in an e"periment to determine
the value of a 0uantity !alled the refra!tive inde" of perspe". he blo!k is pla!ed on a sheet of plain paper that is mounted on a !ork mat. wo pins P4 and P7 are viewed through the blo!k and two additional pins P8 and P9 are stu!k into the mat so that P8, P9 and the images of P4 and P7 appear to be e"a!tly in line, one behind the other. 5a6 5i6 *n >ig. %.1, draw a line through the positions of P8 and P9 and e"tend the line until it meets C<.
Show the path of the ray of light through the blo!k by +oining point E to point F. 5ii6
5ii6
5iii6 6al!ulate the refra!tive inde" n of perspe" using the e0uation E F n @ .% × . ′ N F
n @ PPPPPPPP 36. n
this e/periment 0ou are to investigate reflection in a plane mirror. 6arry out the following instru!tions, referring to >ig.
5a6 he line MMV shows the position of the mirror. 7raw a normal to this line at its !entre. 5b6 5la!e the mirror, with its refle!ting fa!e verti!al, on the line MMV. 5)6 5la!e the !ard so that it stands verti!ally with end = on the normal line and at a distan!e / @ %. !m from the mirror. he !ard must be parallel to the mirror. 5d6 7raw a line from the edge A of the !ard to the point where the normal meets the line <
37. 8 student is investigating the passage of light through a transparent blo!k, as shown in >ig.
he student looks through the blo!k. Fe pla!es pins so that two pins marking the in!ident ray and two pins marking the emergent ray all appear to be e"a!tly one behind the other.
5a6 *n >ig., mark suitable positions for the four pins, two on the in!ident ray and two on the emergent ray. 5b6 5i6 *n >ig. 4.1, draw the normal at point A. 5ii6 *n >ig. 4.1, draw in the line A=.
normal. i @ ..................................... 38. (n this e"periment, you are to determine the fo!al length of a lens.
6arry out the following instru!tions referring to >ig.
5a6 5la!e the lens so that its !entre is 2. !m from the illuminated ob+e!t. 5b6 ig. 5)6 5la!e the s!reen !lose to the lens.
39. 8n (6S- student was investigating the passage of red light through a prism.
>ig.2.1shows the outline of the prism and an in!ident ray.
5a6 ig. 2.1.
i @ PPPPPP. 5b6 he angle of refra!tion as the ray entered side A= of the prism was 22R. 5i6 *n >ig. 2.1, draw in the refra!ted ray from point < as a!!urately as possible. 5ii6 ig.2.1, draw as a!!urately as possible the ray !oming out of the prism. 5d6 8nother student used four opti!s pins to tra!e the passage of a ray through a prism. >ig. 2.2 shows the prism, the position of the studentBs eye and the dire!tions of the ray.
*n >ig. 2.2, show positions of the four opti!s pins, pla!ed to obtain as a!!urate a result as possible.
apparatus is shown in >ig.1.
>ig 1 he ob+e!t is a triangular hole in a s!reen. >ig. 2 shows this, a!tual si:e.
>ig 2 he student set the distan!e u at 3%. !m and moved the s!reen to obtain a sharply fo!used image. he image distan!e v was '2.3 !m. 5a6 5i6 6al!ulate m, the magnifi!ation, using the e0uation
m@
u v
m @ ............................. 5ii6 7raw a diagram of the image, a!tual si:e, for a magnifi!ation m @ 2..
5b6 he image distan!e v is the distan!e from the s!reen to the )ere of the lens. -"plain briefly how you would position a metre rule to obtain an a!!urate value for v. Gou may draw a diagram. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ 41. 8n (6S- student is investigating the refle!tion of light by a plane mirror.
*n >ig, the line MMV shows the position of the mirror that is standing on a sheet of paper. he refle!ting surfa!e of the mirror is verti!al. A= is a !ard that is standing verti!ally and is parallel to the refle!ting surfa!e of the mirror. 5a6 7raw a normal to the mirror su!h that the edge = of the !ard lies on the normal. 5b6
i @ .......................... 5e6 6al!ulate the ratio
/ 0
where 0 @ %. !m, the length of the !ard. / 0
@
......................
5,6 he angle of refle!tion is to be determined as a!!urately as possible. *n >ig, mark with the letters >, Y and the points where the student would pla!e three pins in order to plot the refle!ted ray. 42. (n this e"periment, you are to determine two values of magnifi!ation produ!ed by a
!onverging lens. Gou have been given an illuminated ob+e!t, a !onverging lens mounted in a holder, a s!reen, and a metre rule. he illuminated ob+e!t and the s!reen have been fi"ed to the ben!hY do o ry o )(a&e (eir poiio a ay i"e . 6arry out the following instru!tions referring to >ig.1.
>ig. 1 5a6 5la!e the lens between the illuminated ob+e!t and the s!reen and about % !m away from the illuminated ob+e!t. 5b6
5e6 ig. 4.2.
>ig. 2 5&6 *n!e again, slowly move the lens towards the s!reen until you see a smaller image of the illuminated ob+e!t on the s!reen. 8d+ust the position of the lens until the image is sharply fo!used. 5(6 Dsing the metre rule, measure and re!ord /, the distan!e from the illuminated ob+e!t to the !entre of the lens as shown on >ig. 4.3.
>ig. 3 >ig 4 5i6 ig. 4. 5+6 6al!ulate the ratios u 3 v 0 2 /
3.
& h
5#6 State and briefly e"plain one pre!aution you took in order to obtain reliable measurements.
