The velocity of photons is proportional to (where $\nu=$ frequency)

$A$ photon of wavelength $4400 \, \mathring{A}$ is passing through vacuum. The effective mass and momentum of the photon are respectively

Light of wavelength $5000 \, \mathring{A}$ falls on a sensitive surface. If the surface has received $10^{-7} \, \text{J}$ of energy,then the number of photons falling on the surface will be:

The frequency of a photon having energy $66 \ eV$ is:

$A$ $60 \,W$ source emits monochromatic light of wavelength $662.5 \,nm$. The number of photons emitted per second is

$A$ laser produces a beam of light of frequency $5 \times 10^{14} \,Hz$ with an output power of $33 \,mW$. The average number of photons emitted by the laser per second is (Planck's constant $h = 6.6 \times 10^{-34} \,J \,s$)