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A 200 W sodium street lamp emits yellow light of wavelength 0.6 µm. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is
Options
(a) 1.5 x 10²⁰
(b) 6 x 10¹⁸
(c) 62 x 10²⁰
(d) 3 x 10¹⁹
Correct Answer:
1.5 x 10²⁰
Explanation:
Give that, only 25% ov 200 W converter electrical energy into light of yellow colour
(hc / λ) x N = 200 x 25/100
Where N is the no. of photons emitted per second, h = plank’s constant, c, speed of light
N = 200 x 25 / 100 x λ / hc
= 200 x 25 x 0.6 x 10⁻⁶ / (100 x 6.2 x 10⁻³⁴ x 3 x 10⁸)
= 1.5 x 10²⁰
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Topics: Dual Nature of Matter and Radiation
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Subject: Physics
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Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score
- Shear modulus is zero for
- The oscillation of a body on a smooth horizontal surface is represented by the equation
- Calculate the focal length of a reading glass of a person, if the distance
- If two electric bulbs have 40 W and 60 W ratings at 220 V, then the ratio
- The weight of a body on surface of earth is 12.6 N. When it is raised to a height
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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