Question

Two square reflectors, each 1.85 cm on a side and of mass 4.25 g, are located at opposite ends of a thin, extremely light, 1.00-m rod that can rotate without friction and in a vacuum about an axle perpendicular to it through its center (see figure below). These reflectors are small enough to be treated as point masses in moment-of-inertia calculations. Both reflectors are illuminated on one face by a sinusoidal light wave having an electric field of amplitude 1.50 N/C that falls uniformly on both surfaces and always strikes them perpendicular to the plane of their surfaces. One reflector is covered with a perfectly absorbing coating, and the other is covered with a perfectly reflecting coating. What is the angular acceleration of this device?

Answer 1

Well, momentum transfer of reflected wave is 2 [Energy / c]

Moment of inertia will be I = 2(4.25g) (50cm)^2 but might prefer I units (mks)

Energy flux (watts/area)
could be obtained from Poynting vector S = (1/mu.o) E x B [vector x product].

You will then want to use torque = moment of intertia x angular acceleration.

Hope this helps. I'm soon to bed.

Answer 2

im lost with these multiple equations... :( my hw is due at midnight..

Answer 3

can u help please?