PART TWO. THERMODYNAMICS AND MOLECULAR PHYSICS

Q.262. A laser emits a light pulse of duration ζ = 0.13 ms and

Problems in General Physics

Class 11

IE Irodov

Chapter 1: PART ONE. PHYSICAL FUNDAMENTALS OF MECHANICS

277 questions

Chapter 2: PART TWO. THERMODYNAMICS AND MOLECULAR PHYSICS

9 questions

Q.261. From the standpoint of the corpuscular theory demonstrate that the momentum transferred by a beam of parallel light rays per unit time does not depend on its spectral composition but depends only on the energy flux

Φ_{e}

Q.262. A laser emits a light pulse of duration ζ = 0.13 ms and energy E = 10 J. Find the mean pressure exerted by such a light pulse when it is focussed into a spot of diameter d = 10 pm on a surface perpendicular to the beam and possessing a reflection coefficient ρ = 0.50.

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Chapter 3: PART THREE. ELECTRODYNAMICS

46 questions

Chapter 4: PART FOUR. OSCILLATIONS AND WAVES

155 questions

Chapter 5: PART FIVE. OPTICS

215 questions

Chapter 6: PART SIX. ATOMIC AND NUCLEAR PHYSICS

271 questions

Question

Hard

Solving time: 5 mins

Q.262. A laser emits a light pulse of duration ζ = 0.13 ms and energy E = 10 J. Find the mean pressure exerted by such a light pulse when it is focussed into a spot of diameter d = 10 pm on a surface perpendicular to the beam and possessing a reflection coefficient ρ = 0.50.

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Book:

Problems in General Physics (IE Irodov)

Text solutionVerified

The mean pressure

is related to the force F exerted by the beam by
$\times \frac{π d ^{2}}{4} = F$
The force F equals momentum transferred per second. This is (assuming that photons, not reflected, are absorbed)
$2 ρ \frac{E}{c τ} + (1 - ρ) \frac{E}{c τ} = (1 + ρ) \frac{E}{c τ}$
The first term is the momentum transferred on reflection (see problem (261)); the second on absorption.
$⟨ p ⟩ = \frac{4 ( 1 + ρ ) E}{π d ^{2} c τ}$
Substituting the values we get
$⟨ p ⟩ = 48.3$ atmosphere.

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Question Text	Q.262. A laser emits a light pulse of duration ζ = 0.13 ms and energy E = 10 J. Find the mean pressure exerted by such a light pulse when it is focussed into a spot of diameter d = 10 pm on a surface perpendicular to the beam and possessing a reflection coefficient ρ = 0.50.
Topic	Thermal properties of Matter
Subject	Physics
Class	Class 11
Answer Type	Text solution:1
Upvotes	82

Q.262. A laser emits a light pulse of duration ζ = 0.13 ms and energy E = 10 J. Find the mean pressure exerted by such a light pulse when it is focussed into a spot of diameter d = 10 pm on a surface perpendicular to the beam and possessing a reflection coefficient ρ = 0.50.

Text solutionVerified

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Q.262. A laser emits a light pulse of duration ζ = 0.13 ms and energy E = 10 J. Find the mean pressure exerted by such a light pulse when it is focussed into a spot of diameter d = 10 pm on a surface perpendicular to the beam and possessing a reflection coefficient ρ = 0.50.

Text solutionVerified

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