Experiment 403 Refraction from a spherical surface: Thin Lens aims to determine the focal length of a convex lens using two different methods. One is using different locations of the o!ect and the second is using the graphical method. There are three parts of the experiment" the first part is determining the focal length of the lens in which the light source is in an infinite location from the o!ect. The second part is determination of the focal length using a definite distance assigned in the experiment" and otaining the image and o!ect distance which was proven interchangeale. The last part is otaining the image and o!ect distance with the same set up as the second part of the experiment and plotting it as points to e ale to get the x and # intercepts. The The magnification of image and o!ect si$e was also determined.
Sample Computation
%art &. Trial ':
s
ince :
s
Trial 1:
s
ince :
s
=
s =9.7 cm
&ve )ocal Length * +,.,-,./1 * ,.2 cm
∞ "
f =s '
&ctual )ocal Length * '0 cm
∞ (
s
∞ "
f s '
=
=
'
∞ (
=
'
=
9.9 cm
=
error
=
error
=
10 −9.8 10
× 100
2
Error &nal#sis and ources The error encountered is onl# human error for the memers does not have a ver# clear e#esight especiall# the room was dar therefore the cause of error in the experiment.
%art 5. s =100 cm
Lens ':
(
'
s =11.3 cm f =
( 100 )( 11.3 ) 100 + 11.3
f =10.2 cm error = error
=
10.2
−10
10
× 100
2
Error &nal#sis and ources ame as the first part the error encountered is onl# human error for the memers does not see the image that clearl# in comparison when lights are turned on.
%art 6. '00 cm gap: 1
s
'
s
=0.01 c m−
1
=
26.4
cm (
'
s =73.6 cm (
h1=11 cm (
1
=0.04 c m− ( s 1
s
'07 cm gap: 1
s
25.9 cm
1
−1
'
h1=12.2 cm ; =0.04 c m s
'
h1= 13.3 cm
(
s =79.1 cm (
(
s =84.7 cm (
1
=0.01 c m−
s
=
25.3 cm
1
− = 0.04 c m ( s ( 1
=0.01 c m−
1
'
x −intercept = y − intercept = 1
1
1
1
f
s
s
0.04
= + ' =
1
= 0.05 c m−
+
1
f
1 0.01
1
f
f =20 cm 20 −20
error
=
error
=
20
=
× 100
0
'
m
(
1
'
''0 cm gap:
s
=
s ; m s
%osition ':
h1 =
hO 81.2 ( 1.7
%diff
1.08
83.07 ( 3.07
%diff
0
83.37 ( 3.33
%diff = 0.6
=
=
Conclusion
9n this experiment" it was concluded that a lens is an optical device of circular form that refracts the light passing through it. 9t is made from transparent material that is ounded # two regular surfaces with an index of refraction higher than the surrounding medium. The lens used was a convex meaning a converging lens which is thicer in the middle and thinner at the outer edges and it was also nown that convex focal length is positive. 6onvex lenses have two focal points on oth sides. ue to this the resulting focal point will e the same. 9n addition" two images were formed in using converging lens namel#( the real inverted image and the virtual erected image. &s the experiment was done" the magnification was studied to e the ratio of the image distance and o!ect distance as well as the image height and the
o!ect height. There is alwa#s a distance wherein the image will e as clear as the o!ect in a definite value of distance. The data otained in this experiment have ver# low percentage error lie in part & and 5 where in the percentage error was onl# 1; compared to the actual focal length of the '00 mm lens and a '.17; error in the 100 mm lens. On part 6 of the experiment the results otained gave no error in comparison to the actual value of the focal length of a 100 mm convex lens. Lastl#" when the magnification was compared in computing
