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BITSAT2021PhysicsDual Nature of MatterActual

Monochromatic light of wavelength 667 ~nm is produced by a helium neon laser. The power emitted is 9 ~mW . The number of photons arriving per sec on the average at a target irradiated by this beam is:

Options

  1. A3 10¹⁶
  2. B9 10¹⁵
  3. C3 10¹⁹
  4. D9 10¹⁷

Correct answer

A. 3 10¹⁶

Step-by-step solution

=667 10⁻⁹ m, P =9 10⁻³ ~W P = Nhc , N = No. of photons emitted/sec. N = 9 10⁻³ 667 10⁻⁹ 6.6 10⁻³⁴ 3 10⁸ =3 10¹⁶ / sec

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