JEE Main 2016PhysicsWave OpticsHardMCQ

JEE Main 2016 — Wave Optics Question with Solution

JEE Main 2016 (03 Apr)

Question

The box of a pin hole camera, of length L, has a hole of radius a. It is assumed that when the hole is illuminated by a parallel beam of light of wavelength λ the spread of the spot (obtained on the opposite wall of the camera) is the sum of its geometrical spread and the spread due to diffraction. The spot would then have its minimum size (say bmin ) when:

Choose an option

Show full solutionCorrect option: A
Correct answer
Aa=λL and bmin=4λL

Step-by-step explanation

In diffraction, first minima, we have

sinθ=λa

b=a+Lλa   ...i

Then, minimum size of a spot, we get

∂b∂a=0⇒1-Lλa2=0⇒a=λL   ...ii

So,

 bmin=λL+λL

         =2λL=4λL 

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About this question

This is a previous-year question from JEE Main 2016, covering the Wave Optics chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.