   Chapter 30, Problem 62PE

Chapter
Section
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 100°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 10.6μm . In 1.00ms , this laser raised the temperature of 1.00cm3 of flesh to 100C and evaporated it.

Formula Used:

Energy and change in temperature are related as follows:

E=m(cΔT+Lv)

Where E= Energy

c= Specific heat

ΔT= Change in temperature

Lv= Latent heat of vaporization

Calculation:

Mass of the flesh is calculated as

Density=MassVolume

We have Volume=1cm3=106m3

Density=1000kg/m3

Thus, Mass is given as

Mass=(1000kg/m3)(106m3)

Mass=103kg

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

Thus, we have

c=4186J/kg.C

Lv=2256×103J/kg

ΔT=100C37C=63C

Now, energy is calculated as

E=m(cΔT+Lv)

E=(103kg)[(4186J/kg

To determine

(b)

What was the minimum power output during the flash?

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