Laser recoil (was Re: GEVs/Grav/Arty)

> > ** What recoil do you see from a HEL?

Okay, memory is slowing coming back. As stated above the momentum (p) of a
photon is given by the Planck constant (h) divided by the wavelength (l). The
energy (E) of a photon is given by the Planck constant multiplied by the
frequency (f). And wavelength multiplied by frequency gives the speed of light
(c)

p = h/l
E = h * f c = l * f

So, p = E/c

For a kinetic energy projectile, p = mass (m) * velocity (v) E = 0.5 * m * v^2

So, p = 2 * E/v
(For relativistic particles, the 2 decreases to 1 as v approaches c).

So for a laser 'pulse' with the same energy as a KE projectile the momentum
will be a lot lower. Hence, the recoil will be a lot lower.