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JEE Main201910 Apr 2019Evening ShiftPhysicsDual Nature of MatterActual

A 2 m W laser operates at a wavelength of 500 n m . 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 × 10 8 m / s ]

Options

  1. A1.5 × 10 16
  2. B5 × 10 15
  3. C2 × 10 16
  4. D1 × 10 16

Correct answer

B. 5 × 10 15

Step-by-step solution

P = 2 m W λ = 500 n m Number of photons will be emitted per second is, n = P h c λ = 2 × 10 - 3 × 500 × 10 - 9 6.6 × 10 - 34 × 3 × 10 8 = 5 × 10 15

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