JEE Main 2019PhysicsDual Nature of MatterEasyMCQ

JEE Main 2019 — Dual Nature of Matter Question with Solution

JEE Main 2019 (10 Apr Shift 2)

Question

A 2 mW laser operates at a wavelength of  500 nm . The number of photons that will be emitted per second is:
[Given Planck's constant h=6.6×10-34 J s, speed of light  c=3.0×108 m/s ]

Choose an option

Show full solutionCorrect option: B
Correct answer
B5×1015

Step-by-step explanation

P=2 mW
λ=500 nm
Number of photons will be emitted per second is,
n=Phcλ=2×10-3×500×10-96.6×10-34×3×108
=5×1015

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About this question

This is a previous-year question from JEE Main 2019, covering the Dual Nature of Matter 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.