Chapter 30, Problem 62PE

### 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

# Integrated ConceptsA carbon dioxide laser used in surgery emits infrared radiation with a wavelength of 10.6 μm . In 1.00 ms, this laser raised the temperature of 1.00 cm3 of flesh to 100Â°C and evaporated it.(a) How many photons were required? You may assume flesh has the same heat of vaporization as water. (b) What was the minimum power output during the flash?

To determine

(a)

The number of photons required.

Explanation

Given Data:

Given that carbon dioxide laser used in surgery emits infrared radiation with a wavelength of 10.6Î¼m . In 1.00ms , this laser raised the temperature of 1.00cm3 of flesh to 100âˆ˜C and evaporated it.

Formula Used:

Energy and change in temperature are related as follows:

â€ƒâ€ƒE=m(cÎ”T+Lv)

Where E= Energy

â€ƒâ€ƒc= Specific heat

â€ƒâ€ƒÎ”T= Change in temperature

â€ƒâ€ƒLv= Latent heat of vaporization

Calculation:

Mass of the flesh is calculated as

â€ƒâ€ƒDensity=MassVolume

We have Volume=1cm3=10âˆ’6m3

â€ƒâ€ƒDensity=1000kg/m3

Thus, Mass is given as

â€ƒâ€ƒMass=(1000kg/m3)(10âˆ’6m3)

â€ƒâ€ƒMass=10âˆ’3kg

Assume that heat capacity and latent heat of vaporization of flesh is same as that of water.

Thus, we have

â€ƒâ€ƒc=4186J/kg.âˆ˜C

â€ƒâ€ƒLv=2256Ã—103J/kg

â€ƒâ€ƒÎ”T=100âˆ˜Câˆ’37âˆ˜C=63âˆ˜C

Now, energy is calculated as

â€ƒâ€ƒE=m(cÎ”T+Lv)

â€ƒâ€ƒE=(10âˆ’3kg)[(4186J/kg

To determine

(b)

What was the minimum power output during the flash?

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