1. The speed of light in a certain substance is 88% of its value in water. What

Question

1. The speed of light in a certain substance is 88% of its value in water. What is the index of refraction of that substance?

2. A glass surface (n = 1.50) has a layer of water (n = 1.33) on it. Determine the critical angle for the glass to water interface.

3. In a slide or movie projector, the film acts as the object whose image is projected on to the screen. A 105 mm focal length lens is to project an image on a screen 6.5 m away.

a. how far from the lens the slide should be.

b. Of the slide is 36 mm wide, how wide will the picture be on the screen?

Explanation / Answer

1

The speed of light in water (where index of refraction is 1.33) is:

v = c/n
= 3.0 x 10^8m/s / 1.33
= 2.3 x 10^8m/s

Therefore:

v = c / n
n = c / v
= 3.0 x 10^8m/s / 0.88(2.3 x 10^8m/s)
n = 1.477

2

sin(C) = 1.33 / 1.51
C = 61.7 deg

3

Following is the process, just calculate the value

1/f= 1/do + 1/di rearrange

1/do = 1/f - 1/di

do is distance from object
di is distance from image (given as 6.5m)
f is the focal length (given as 105)

have to convert 6.5 m to milimeter = 6500

1/do = 1/105 - 1/6500

part 2

m=-di/do=hi/ho

solve for m using m= -di/do

then use m=hi/ho rearrange

hi=(m)(ho)
you are given ho as 36mm
your answer will be in mm but it wants it in meters so divide your answer by 1000

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