Chapter 29, Problem 37PE

### College Physics

1st Edition
Paul Peter Urone + 1 other
ISBN: 9781938168000

Chapter
Section

### College Physics

1st Edition
Paul Peter Urone + 1 other
ISBN: 9781938168000
Textbook Problem

# Construct Your Own ProblemConsider a laser pen. Construct a problem in which you calculate the number of photons per second emitted by the pen. Among the things to be considered are the laser pen's wavelength and power output. Your instructor may also wish for you to determine the minimum diffraction spreading in the beam and the number of photons per square centimeter the pen can project at some large distance. In this latter case, you will also need to consider the output size of the laser beam, the distance to the object being illuminated, and any absorption or scattering along the way.

To determine

The construction of a problem in which the number of photons per second emitted by a laser pen is calculated.

Explanation

Formula used:

The energy and the number of photons are related by the formula,

â€ƒâ€ƒE=nhcÎ»

Calculation:

Consider a laser pen of power 2.0â€‰mW and emitted light of wavelength 630â€‰nm .

The energy of photons emitted per second is given as,

â€ƒâ€ƒEt=(nt)hcÎ»P=(nt)hcÎ»nt=PÎ»hc

By substituting the values, we get

â€ƒâ€ƒnt=2

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