FISA DE LUCRU-Reflexie totala si refractie-experimente

FIȘĂ DE LUCRU Reflexia si refractia luminii

1) Indicele Indicele de refrac refracție al unui mediu mediu omoge omogenn și izotro izotropp poate poate fi fi exprim exprimat at cu relația: a) n!"c# $) nc"!# c) n ! c# %) Lumina Lumina se propag& propag& din aer aer 'n sticl&( Reprez Reprezenta entarea rea corect& corect& a mersului mersului razelor razelor de lumin& este: aer 

aer 

a)

# $) sticl&

aer 

# c) sticl&

sticl&

) Imaginea Imaginea unui unui peste situat situat pe fundul fundul apei* apei* !azut !azut de un pescar* pescar* este: este: a) real&# $) !irtual& c)mai mare decat in realitate d) mai mica decat in realitate +) In figurile figurile urmatoare urmatoare am trasat trasat mersul mersul razelor razelor de lumina lumina intr,o lama lama de sticla cu o anumita grosime( Care desen este corectaer

aer  n

n

aer

aer

Corecta Corectați repreze reprezent&ri nt&rile le gre greșite( .ustifica .ustificati/ ti/

0) Dac& Dac& o oglin oglind& d& plan& plan& se rote rotește cu ung ungiu iull 2* raza raza refle reflecta ctat& t& se rote rote ște cu: cu: a) 34 # $) 2 # c) %2

5) Un copil copil pri!e pri!ește normal normal o piatr& piatr& aflat& aflat& pe fundul fundul unui unui lac și o !ede la ad6nc ad6ncimea imea 1*% m( 7n realitate* piatra se afla la ad6ncimea: a) 3*8m # $) 1*%m # c) 1*+m # d) 1*5m

9nap&+")

Fisa de activitate experimentala  Reflexia totala

Theory

ur $rains assume tat te ligt from te o$;ects tra!els in a straigt pat to our ee can $e fooled $< refraction and total internal reflection $ecause an o$;ect appears in a certain place?or does not appear at all?onl< $ecause te ligt raen pond* ere te roc@ appears to $e(  But , that is not where the rock actually is.

 Fig

 If ere farter off to te side of te roc@ so tat ere at a great enoug angle to it*
>ould not see te roc@ at all $ecause of total internal reflection(

 Fig

Material

 penn< >ater # Buarter # large* clear drin@ing glass Procedure 1. et te Buarter on te ta$le( 2. et a large clear glass on top of te coin( $ser!e te coin troug te side of te

glass( Is te coin !isi$le3. ile atc te coin troug te side of te glass* fill te glass >it >ater( at appens to te image of te coin4. Loo@ o!er te top of te glass( Do not loo@ at te actual coin* >ic sould no>  $e !isi$le troug te $ottom of te glass( Instead* loo@ at te opposite* interior  side of te glass( Record at from te side and from te top of te clear glass >en it >as filled >it >ater( =r< to dra> a diagram to explain >at ( 9int: =e glass,air $oundar< is important ere ( =e speed of ligt is fastest in air* muc slo>er in >ater* and slo>est in glass( Refraction also pla
figura

What’s Going On

=e coin is clearl< !isi$le troug te side of te emptere it actuall< lies?despite refraction at air,glass and glassair $oundaries 9see figure)( =ere is air  $ot inside and outside te glass* so te ligt is $ent first to>ard te perpendicular and ten a>a< from it( ince te glass is so tin?and tis occurs $ot at te $ottom of te glass and at te side?te ligt is onl< sligtl< de!iated from its original pat* and
Fig

=e coin disappears >en te glass is filled >it >ater 9see figure)( =e ligt raater are first refracted at te >ater,glass 9fasterto, slo>er) $oundar<( Ht te glass,air  9slo>er,to,faster) $oundar< on te side of te glass* total internal reflection ta@es place( =us* no ligt from te coin reaces
Fig

Seeing Multiples

Loo@ing o!er te top of te glass* ere totall< reflected at te glass,air $oundar< on te opposite side of te glass and ten refracted to>ard te eater,air $oundar<( Hn image of te coin >as terefore !isi$le( =e coin is !isi$le from te top of te glass 9pat 1)( Hn image of te coin in te opposite side is also !isi$le $ecause of te effects of refraction and total internal reflection 9pat %)(

fig

Connections

en a ligt ra< stri@es a slo>er,to,faster $oundar< at an angle to te perpendicular  greater tan a certain !alue 9for >ater to air a$out +8 degrees)* instead of normal refraction* a related optic penomenon occurs: total internal reflection. =e ligt ra< is completel< reflected off te $oundar< * and none of te ligt passes troug( In tis procedure*