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In the 25 ftft Space Simulator facility at NASA's Jet Propulsion Laboratory, a bank of overhead arc lamps can produce light of intensity 2500 W/m^2 at the floor of the facility. (This simulates the intensity of sunlight near the planet Venus.)

Required:
Find the average radiation pressure (in pascals and in atmospheres) on

a. A totally absorbing section of the floor.
b. A totally reflecting section of the floor.
c. Find the average momentum density (momentum per unit volume) in the light at the floor.

Respuesta :

tochjosh

Answer:

a) 8.33 x [tex]10^{-6}[/tex] Pa  or  8.22 x [tex]10^{-11}[/tex] atm

b) 1.66 x [tex]10^{-5}[/tex] Pa  or  1.63 x [tex]10^{-10}[/tex] atm

c) 2.77 x [tex]10^{-14}[/tex] kg/m^2-s

Explanation:

Intensity of light = 2500 W/m^2

area = 25 ft^2

a) average radiation pressure on a totally absorbing section of the floor[tex]Pav = \frac{I}{c}[/tex]

where I is the intensity of the light

c is the speed of light = [tex]3*10^{8} m/s[/tex]

[tex]Pav = \frac{2500}{3*10^{8} }[/tex] = 8.33 x [tex]10^{-6}[/tex] Pa

1 pa = [tex]9.87*10^{-6}[/tex]

8.33 x [tex]10^{-6}[/tex] Pa = 8.22 x [tex]10^{-11}[/tex] atm

b) average radiation for a totally radiating section of the floor

[tex]Pav = \frac{2I}{c}[/tex]

this means that the pressure for a totally radiating section is twice the average pressure of the totally absorbing section

therefore,

Pav = 2 x 8.33 x [tex]10^{-6}[/tex]  = 1.66 x [tex]10^{-5}[/tex] Pa

or

Pav in atm = 2 x 8.22 x [tex]10^{-11}[/tex] = 1.63 x [tex]10^{-10}[/tex] atm

c) average momentum per unit volume is

[tex]m = \frac{I}{c^{2} }[/tex]

[tex]m = \frac{2500}{(3*10^{8}) ^{2} }[/tex] = 2.77 x [tex]10^{-14}[/tex] kg/m^2-s