Practice portal › Ray Optics and Optical Instruments › Refraction through a Prism
Asked in RS Academy GUJCET booklet · Deviation and minimum deviation
Given: a right-angled prism of refracting angle A = 4° and n = 1.5; the incident ray is horizontal and so meets the vertical face square on.
Idea: take the two refracting faces one at a time.
At the first face the ray travels along the normal, so it enters without bending: r₁ = 0.
For any prism r₁+r₂ = A, so inside the glass the ray meets the slanted face at r₂ = 4° to its normal.
Snell's law at that face, going from glass into air: n sin r₂ = sin e, so sin e = 1.5×sin 4° = 1.5×0.0698 = 0.1047.
e = 6°, and as a check the deviation is e-r₂ = 2°, which is just A(n-1) = 4°×0.5 for a thin prism.
Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.
Practise this with a timer