Photon momentum and uses of the photoeffect
Answers are for parents and teachers.
1
A photon has wavelength 220 nm. What is its momentum? (h = 6.6·10⁻³⁴ J·s)
3·10⁻²⁷ kg·m/s
2
Light of intensity 1200 W/m² falls on a fully absorbing surface. What is the pressure? (c = 3·10⁸ m/s)
4·10⁻⁶ Pa
3
If the same light falls on a fully reflecting surface, what is the pressure?
8·10⁻⁶ Pa
4
Eight solar cells of emf 0.5 V each are connected in series. What is the total emf in V?
4
5
Why do we not notice light pressure in everyday life?
In p = I/c the speed c = 3·10⁸ m/s is huge, so the pressure is only millionths of a pascal.