Index of Refraction & Snell’s Law Questions
Make sure to show all of your work! Each question would be worth 5
marks!
1. Calculate the speed of light for the following mediums:
a. Water (n=1.33); 2.26 x 108 m/s
b. Diamond (n=2.42) 1.24x108 m/s
c. Plexiglas (n=1.51) 1.99x108 m/s
2. Calculate the refractive index for a substance if the speed of light in
that medium is
a. 2.1 x 108 m/s= 1.43
b. 1.5 x 108 m/s= 2.0
3. Calculate the speed of light in a hypothetical material you have
discovered and named in honour of yourself. Its refractive index is
0.90.
a. V=3.00x108/0.90= 3.33 x 108 m/s
4. Calculate the angle of refraction for light as it passes from air to
each of the mediums;
sin25=0.42
a. Water (n=1.33); sinr=sini/n sinr=0.42/1.33 sinr=0.31 r=18.4°
b. Diamond (n=2.42) sinr=sini/n sinr=0.42/2.42 sinr=0.17
r=10°
c. Plexiglas (n=1.51) sinr=sini/n sinr=0.42/1.51 sinr=0.28
r=16.1°
At an incidence angle of 25°.
5. An angle of incidence of 20° in water results in an angle of
refraction of 15°.
a. Is the second medium more of less optically dense than the
first medium? Second one because it bends towards the normal
since the angle is less we know it is closer to the normal.
b. Find the n of the second medium n=0.34/0.26=1.31
c. Find the speed of light in each medium
i. 3.00x108/1.31=2.29x108(second medium)
ii. 3.00x108/0.76=3.95x108(first medium)
d. Repeat this question for an angle of refraction of 25°
i. With the new angle of refractionthe light is moving
away from the normal so it is less dense than water
ii. n=0.34/0.42=0.81
iii. speed of light in each medium
3.00x108/0.81=3.70x108(second medium)
3.00x108/1.23=2.44x108(first medium)