In the 25 ft Space Simulator facility at NASA\'s Jet Propulsion Laboratory, a ba

Question

In the 25 ft Space Simulator facility at NASA's Jet Propulsion Laboratory, a bank of overhead are 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.) Assume that the actual intensity is 2360 W/m^2 for this problem. (a) Find the average radiation pressure (in pascals and in atmospheres) on a totally absorbing section of the floor. 8.33E-6 pa 8.23E-11 atm (b) Repeat for a totally reflecting section of the floor. Pa atm (c) Find the average momentum density (momentum per unit volume) in the light at the floor. kg/m^2 middot s

Explanation / Answer

a)When the wave is totally absorbed:

P = I/c

P = 2360 W/m^2/ 3 x 10^8 = 7.86 x 10^-6 Pa

P = 7.86 x 10^-6 Pa = 7.76 x 10^-11 Pa

Hence, P = 7.86 x 10^-6 Pa ; P = 7.76 x 10^-11 Pa

b)When the wave is totally reflected,

P = 2I/c

P = 2 x 2360/3 x 10^8 = 1.57 x 10^-5 Pa

P = 1.57 x 10^-5 Pa = 1.55 x 10^-10 Pa

Hence, P = 1.57 x 10^-5 Pa ; P = 1.55 x 10^-10 Pa

c)P = I/c^2

P = 2360/(3 x 10^8)^2 = 2.62 x 10^-14 kg/m^2-s

Hence, P = 2.62 x 10^-14 kg/m^2-s

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