In the given figure, a parallel beam of light is incident on the upper part of a prism with an angle of 1. 8 ∘ and a refractive index (R.I.) of 3/2 . The light emerging from the prism falls on a conca

Question

In the given figure, a parallel beam of light is incident on the upper part of a prism with an angle of $1. 8^{\circ}$ and a refractive index (R.I.) of $3/2$ . The light emerging from the prism falls on a concave mirror with a radius of curvature of $20 c m$ . The distance of the point (where the rays are focused after reflection from the mirror) from the principal axis is: [use $π = 3.14$ ]

TestHub · Accepted Answer

The deviation produced by the prism is δ = A ( μ − 1 ) = 1. 8 ∘ ( 2 3 ​ − 1 ) = 0. 9 ∘ . This deviation is small, so tan δ ≈ δ (in radians). δ = 0.9 × 180 π ​ r a d = 0.9 × 180 3.14 ​ = 0.0157 r a d . The focal length of the concave mirror is f = 2 R ​ = 2 20 ​ = 10 c m . The distance of the focus from the principal axis is y = f tan δ ≈ f δ = 10 × 0.0157 = 0.157 c m .

Physics - Geometrical Optics Question with Solution | TestHub

Options:

Doubts & Discussion

JEE Main (2026)

JEE Main (2027)