δmin=2i−A
A=2i−A
A=i
μ=sin(2A)sin(2δmin+A)=sin(2A)sin(A)=sin30∘sin60∘
μ=3
v=μc=33×108ms−1
t=vAP=(33×108)53×10−2=5×10−10s
So, x=5
JEE Main 2021 — Physics Optics
2021integerhard
Cross-section view of a prism is the equilateral triangle ABC shown in the figure. The minimum deviation is observed using this prism when the angle of incidence is equal to the prism angle. The time taken by light to travel from P (midpoint of BC) to A is ___________ ×10−10s. (Given, speed of light in vacuum =3×108ms−1 and cos30∘=23)
Official previous-year question
Held on 31 Aug 2021 · Verified 6 Jul 2026.
Did you get this right?
Sign in to track your attempts and accuracy.
Your note
Sign in to keep a private note on this question. Nothing you write is ever public.
JEE Main Optics in other years
More JEE Main Optics questions
When an unpolarized light falls at a particular angle on a glass plate (placed in air), it is observed that the reflected beam is linearly polarized. The angle of refracted beam with respect to the normal is $\_\_\_\_$. $\left(\tan ^{-1}(1.52)=57.7^{\circ}\right.$, refractive indices of air and glass are 1.00 and 1.52, respectively.)
2026medium
In Young's double slit experiment, the fringe width is β. If the wavelength of light is doubled and the slit separation is halved, the new fringe width is:
2026medium
A biconvex lens is formed by using two thin planoconvex lenses, as shown in the figure. The refractive index and radius of curved surfaces are also mentioned in figure. When an object is placed on the left side of lens at a distance of 30 cm from the biconvex lens, the magnification of the image will be : 
2026hard
A collimated beam of light of diameter 2 mm is propagating along $x$-axis. The beam is required to be expanded in a collimated beam of diameter 14 mm using a system of two convex lenses. If first lens has focal length 40 mm, then the focal length of second lens is $\_\_\_\_$ mm.
2026medium
Light ray incident along a vector $\vec{AO}$ $(\vec{AO} = 2\hat{i}-3\hat{j})$ emerges out along vector $\vec{OB}$ $(\vec{OB} = C\hat{i}-4\hat{j})$ as shown in the figure below. The value of $C$ is ________. 
2026medium
Other Physics topics for JEE Main
Keep practicing Optics
Work through every JEE Main Optics PYQ, year by year.