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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
- A plane electromagnetic wave of frequency 20 MHz travels through a space along
- A string in musical instrument is 50 cm long and its fundamental frequency is 800 Hz.
- The time period of a thin bar magnet in Earth’s magnetic field is T
- A bar magnet has a coercivity of 4×10³ Am⁻¹. It is placed inside a solenoid
- A current of 2A flows through a 2Ω resistor when connected across a battery
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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