Light of intensity $10^{-10} \ W/m^2$ and wavelength $5.6 \times 10^{-7} \ m$ is incident on a surface of area $10^{-6} \ m^2$. What is the number of photons incident per second?

The radiant energy from the Sun incident on the Earth's surface is $2 \ cal/cm^2 \cdot min$. If the average wavelength of solar radiation is $5500 \ \mathring A$,then the number of photons incident per minute on a surface area of $1 \ cm^2$ on the Earth's surface is ............ $(h = 6.6 \times 10^{-34} \ J \cdot s, 1 \ cal = 4.2 \ J)$

$A$ $100\,W$ light source is emitting radiation of wavelength $5000\,\mathring{A}$. The rate of emission of photons is of the order of:

$A$ photon has a wavelength of $3 \,nm$. Its momentum and energy, respectively, will be:
$[h = 6.63 \times 10^{-34} \,Js, c = 3 \times 10^8 \,m/s]$

The energy of a photon of light of wavelength $450 \ nm$ is

The ratio of the energy of a photon with $\lambda = 150\,nm$ to that with $\lambda = 300\,nm$ is