JEE Main 2017PhysicsDual Nature of MatterMediumMCQ

JEE Main 2017 — Dual Nature of Matter Question with Solution

JEE Main 2017 (09 Apr Online)

Question

A laser light of wavelength 660 nm is used to weld Retina detachment. If a laser pulse of width 60 ms and power 0.5 kW is used, the approximate number of photons in the pulse are (Take Planck's Constant, h=6.62×10−34 J s)

Choose an option

Show full solutionCorrect option: C
Correct answer
C1020

Step-by-step explanation

The energy of photon is given by E=hcλ.

PowerP is given as, P=Et=nhcλt

From the above equation, the number of photons is n=Pλthc

=0.5×103×660×10-9×60×10-36.6×10-34×3×108

Hence, number of photons in the pulse are=100×1018=1020.

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About this question

This is a previous-year question from JEE Main 2017, 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.