Question

A thin flashlight beam traveling in air strikes a glass plate at an angle of 52° with the plane of the surface of the plate. If the index of refraction of the glass is 1.4, what angle will the beam make with the normal in the glass?

Answer 1

To solve this problem it is necessary to apply Snell's law and thus be able to calculate the angle of refraction.

From Snell's law we know that

`n_1sin\theta_1 = n_2 sin\theta_2`

Where,

n_i = Refractive indices of each material

`\theta_1` = Angle of incidence

`\theta_2` = Refraction angle

Our values are given as,

`\theta_1 = 38\°`

`n_1 = 1`

`n_2 = 1.4`

Replacing

`1*sin38 = 1.4*sin\theta_2`

Re-arrange to find
`\theta_2`

`\theta_2 = sin^(-1) (sin38)/(1.4)`

`\theta_2 = 26.088°`

Therefore the angle will the beam make with the normal in the glass is 26°