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Physics · Geometrical Optics

JEE Advanced 2022 — Paper 1 — Question 30

Three plane mirrors form an equilateral triangle with each side of length L.

There is a small hole at a distance l>0l>0 from one of the corners as shown in the figure. A ray of light is passed through the hole at an angle

θ\theta and can only come out through the same hole. The cross section of the mirror configuration and the ray of light lie on the same plane.

Which of the following statement(s) is(are) correct?

Question figure
  1. Option A:

    The ray of light will come out for θ=30∘\theta=30^{\circ}, for 0<l<L0<l<\mathrm{L}.

    Correct
  2. Option B:

    There is an angle for l=L2l=\frac{L}{2} at which the ray of light will come out after two reflections.

    Correct
  3. Option C:

    The ray of light will NEVER come out for θ=60∘\theta=60^{\circ}, and l=L3l=\frac{L}{3}

  4. Option D:

    The ray of light will come out for θ=60∘\theta=60^{\circ}, and 0<l<L20<l<\frac{L}{2} after six reflections.

Answer: A, B

Step-by-step solution

For option ' A ' there will be normal incidence and ray retrace its path.

For option 'B'

Solution figure

Answer key and solution verified before publishing.

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Exam
JEE Advanced 2022
Paper
Paper 1
Subject
Physics
Chapter
Geometrical Optics
Topic
Reflection of Light and Plane Mirrors

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