Exams › JEE Main › Physics

A prism is placed in air. If a ray is incident at 60° and the prism angle, the deviation angle δ, and the angle of emergence e are all equal, what is the refractive index of the prism?

1. 1.73
2. 1.15
3. 1.5
4. 1.33

Correct answer: 1.73

Solution

With angle of incidence = emergence = 60 deg and A = delta = e, the prism is in symmetric (minimum-deviation) configuration with A = 60 deg, delta = 60 deg. n = sin((A+delta)/2)/sin(A/2) = sin60/sin30 = 0.866/0.5 = 1.73.

Related JEE Main Physics questions

• A telescope is fitted with an objective lens of focal length 100 cm and an eyepiece of focal length 5 cm. If the final image is adjusted to form at the least distance of distinct vision, what is the telescope’s magnifying power?
• An object placed 2.4 m in front of a lens produces a clear image on a film located 12 cm behind the lens. A 1 cm thick glass slab of refractive index 1.50 is then inserted between the lens and the film, with its plane surfaces parallel to the film. To obtain a sharp image again on the film, to what distance from the lens must the object be moved?
• A light ray is incident on an equilateral prism in such a way that the angle of incidence equals the angle of emergence, and this common angle is three-fourths of the prism angle. What is the angle of deviation produced?
• A glass lens with refractive index 1.60 has a focal length of +20 cm when placed in air. If the same lens is immersed in water of refractive index 1.33, its focal length will be
• A person’s farthest point of clear vision is 30 cm from his eyes. If he wants to read a book held 50 cm away, what power of lens should he use?
• An object is kept 40 cm in front of a concave mirror whose focal length is 20 cm. The image formed will be

⚔️ Practice JEE Main Physics free + battle 1v1 →