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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 second on the average at a large irradiated by this beam is:
Options
(a) 3 x 10¹⁶
(b) 9 x 10¹⁵
(c) 3 x 10¹⁹
(d) 9 x 10¹⁷
Correct Answer:
3 x 10¹⁶
Explanation:
λ = 667 x 10⁻⁹ m, P = 9 x 10⁻³ W
P = Nhc / λ, N = no. of photons emitted/sec.
N = (9 x 10⁻³ x 667 x 10⁻⁹) / (6.6 x 10⁻³⁴ x 3 x 10⁸)
= 9 x 6.67 x 10⁻¹⁰ / 3 x 6.6 x 10⁻²⁶
3 x 10¹⁶ / sec
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Topics: Dual Nature of Matter and Radiation
(150)
Subject: Physics
(2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- An a.c. supply gives 30 volt r.m.s which passes through a 10Ω resistance.
- The refractive index of water, glass and diamond are 1.33, 1.50, 2.40 respectively
- A sample of radioactive element has a mass of 10 gram at an instant t=0.
- The ratio of amplitude of magnetic field to the amplitude of electric field for
- Current in a coil changes from 4 A to zero in 0.1 second and the emf induced is 100V
Topics: Dual Nature of Matter and Radiation (150)
Subject: Physics (2479)
Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
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