Which one of these is non-divisible?

The momentum of a photon of light of frequency $f$ is . . . . . . .

When a photon enters glass from air,which one of the following quantities does not change?

Find the number of photons emitted per second by a $100\, W$ red light source. Assume for simplicity that the average wavelength of each photon is $694\, nm$.

Bose-Einstein statistics is applicable to particles with

$A$ parallel beam of light of wavelength $900 \, nm$ and intensity $100 \, W/m^2$ is incident on a surface perpendicular to the beam. The number of photons crossing $1 \, cm^2$ area perpendicular to the beam in one second is: