Question

A ray of light traveling in air strikes a flat 2.00 cm thick block of glass (n = 1.50) at an angle of 19.0 ◦ with the normal.?

a) Trace the light ray through the glass, and find the angle of refraction for light passing from air to glass. Answer in units of ◦.
b) Find the angle of refraction for light passing from glass to air. Answer in units of ◦.

Answer 1

(a).
`\theta_2 = 12.5^o`

(b).
`\theta_1 = 19.0^o`

Step-by-step explanation:

(a).

Snell's law says

`n_1sin(\theta_1) = n_2sin(\theta_2)`

which in our case gives

`(1.00)sin(19.0^o) = (1.50)sin(\theta_2)`

Solving for
`\theta_2` gives

`((1.00)sin(19.0^o))/(1.50) = sin(\theta_2)`

`\theta_2 = sin^(-1)[((1.00)sin(19.0^o))/(1.50)]`

`\boxed{\theta_2 = 12.5^o}`

which is the angle of refraction from air to glass.

(b).

When the light ray goes from glass to back to air again, the angle of refraction equals the angle with which it had entered the glass because of the symmetry in Snell's law:

`(1.00)sin(\theta_1) = (1.50)sin(12.5^o)`

`\boxed{\theta_1 = 19.0^o}`

The result is that the outgoing ray (one that refracted out from glass to air) and the tracing of the incoming ray (one that refracted into the glass) are parallel to each other.