In a space lab a 25 cm^2 sheet of aluminum foil having mass 6.7 x 10^-6 kg is su
ID: 3893029 • Letter: I
Question
In a space lab a 25 cm^2 sheet of aluminum foil having mass 6.7 x 10^-6 kg is subjected to a laser beam of intensity 100 W/m^2 on one side and to a beam of intensity 60 W/m^2 on the opposite side, the radiation in each case hitting with normal incidence. If both of the aluminum foil sides are considered to be totally reflective and the foil is floating in the space lab, what acceleration of the foil will result from the net force from the incident beams?
b. 1.0 x 10^-4 m/s^2
c. 1.5 x 10^-4 m/s^2
d. 4.0 x 10^-4 m/s^2
Explanation / Answer
surface of a target, if the wave is completely reflected then
radiation pressure P= 2*Ef/c
where P is pressure, Ef is energy flux (intensity) in W/m2, c is speed of light in vacuum
net force on sheet =ma=(pa-p'a)=2(E-E')a/c
=2(100-60)*25x10^-4/(3*10^8)
= 6.68x10^-10
a=(6.68x10^-10)/(6.7x10^-6)=1x10^-4 m/s^2