Snell’s Law Questions/ Answers

Indices of Refraction for Various Media:

Medium	Index of Refraction (n)
Air/vacuum	1.00
Ice	1.31
Water	1.33
Ethyl alcohol	1.36
Vegetable oil	1.47
Acrylic	1.49
Glass	1.52
Diamond	2.42

1. Using Snell’s law, determine the constant when the angle of incidence and the angle of refraction are:

a) 50˚ and 30˚                       b) 30˚ and 18˚                       c) 60˚ and 38˚

2. a) What is the angle of refraction in a medium if the angle of incidence in air is 48˚ and the index of refraction of the medium is 1.58?

b) What is the angle of incidence in a medium in the case where the angle of refraction in air is 40˚ and the index of refraction of the medium is 1.58?

3. A ray of light passes from air into water at an angle of incidence of 50˚.  What is the angle of refraction?  (HINT: You will need to use the sin^-1 function on your calculator).

4. Light travels from air into water.  If the angle of refraction is 30˚, what is the angle of incidence?

5. A ray of light in air strikes a block of quartz at an angle of incidence of 30˚.  The angle of refraction is 20˚.  What is the index of refraction in quartz?

6. One ray of light in air strikes a diamond and another strikes a piece of fused quartz.  In each case the angle of incidence is 40˚.  What is the difference in the angles of refraction?

7. An underwater swimmer looks up toward the surface of the water on a line of sight that makes an angle of 25˚ with a normal to the surface of the water.  What is the angle of incidence in air for the light rays that enter the swimmer’s eye?

8. What is the critical angle for light rays passing from:

a) glass into air         b) glass into water

9. In each of the following questions, the second medium is air.

a) What is the critical angle if the index of refraction for a medium is 1.68?

b) What is the index of refraction of a medium if the critical angle is 40˚?

10. Several transparent liquids are carefully poured, one after another, into a glass container, as illustrated.  Each liquid is immiscible (will not mix) air (n = 1.00)

with its neighbour.  A ray of light, with an angle of incidence in oleic acid (n = 1.43)

the glass is 10˚, is projected up through the liquids. water (n = 1.33)

What will be the angle of refraction in air? carbon disulphide (n = 1.46)

Answers:

1.  a) 1.53       b) 1.62            c) 1.41

2.  a) 28˚         b) 24˚

3.  35˚

4.  42˚

5.  1.46

6.  11˚

7.  34˚

8.  a) 41˚         b) 61˚

9.  a) 37˚         b) 1.56

10. 15˚