The photoelectric effect involves absorption of an X-ray photon and ejection of an electron from an atom, a primary mechanism for electron ejection.

Using radar Doppler shift Δf = (2v/c)f, v = Δf·c/(2f) = 2800·3e8/(2·840e6) ≈ 500 m/s = 0.5 km/s.

When a carrier is modulated by an information signal the output is called a modulated carrier wave.

Blackbody spectral distribution versus wavelength rises to a peak and then falls, so the radiant energy initially increases then decreases with wavelength.

At intermediate photon energies, Compton scattering is the dominant interaction between photons and matter.

Fluorescence is the emission of light by a substance that has absorbed electromagnetic radiation, typically at a different (longer) wavelength.

X-rays and gamma-rays are both electromagnetic radiation; they differ in origin but are similar in nature as photons.

Laser light is a highly monochromatic form of electromagnetic radiation.

Shorter wavelength means higher photon energy, so the maximum kinetic energy and thus stopping potential increase.

Photoelectric emission requires photons with sufficient energy to overcome the work function; ultraviolet photons have higher energy than IR, microwaves or radiowaves.