Find the number of photons emitted per second by a $100 \ W$ bulb emitting light of wavelength $540 \ nm$. (Given: $h = 6 \times 10^{-34} \ J \cdot s$)

The minimum intensity of light that can be perceived by the human eye is $10^{-10} \ W/m^2$. If the area of the pupil is $10^{-6} \ m^2$ and the wavelength of light is $560 \ nm$,approximately how many photons per second enter the eye? (Use $h = 6.6 \times 10^{-34} \ J \cdot s$ and $c = 3 \times 10^8 \ m/s$).

The momentum of a photon with energy $20 \, eV$ is

If we express the energy of a photon in $KeV$ and the wavelength in $\mathring{A}$,then the energy of a photon can be calculated from the relation:

The radiation with frequency $1.0 \times 10^{14} \ Hz$ lies in the infrared region. The energy of one photon of this radiation in joules is:

$A$ photon falls through a height of $1 \, km$ in the earth's gravitational field. To calculate the change in its frequency,take its mass to be $h \nu / c^{2}$. The fractional change in frequency $\nu$ is close to