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Question: Answered & Verified by Expert
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 ]
PhysicsDual Nature of MatterJEE MainJEE Main 2019 (10 Apr Shift 2)
Options:
  • A 1.5×1016
  • B 5×1015
  • C 2×1016
  • D 1×1016
Solution:
1601 Upvotes Verified Answer
The correct answer is: 5×1015
P=2mW
λ=500nm
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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