If the mean wavelength of light radiated by a $100 \ W$ lamp is $5000 \ \mathring{A}$,then the number of photons radiated per second is:

$A$ radio transmitter operates at a frequency of $880 \, kHz$ and a power of $10 \, kW$. The number of photons emitted per second is:

The energy flux of sunlight reaching the surface of the earth is $1.388 \times 10^{3} \; W/m^{2}$. How many photons (nearly) per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average wavelength of $550 \; nm$.

The energy of a photon with a wavelength of $6.20 \times 10^{-5} \ cm$ is ....... $eV$.

What is called as the quantum of energy? What is its energy?

The minimum intensity of light to be detected by the human eye is $10^{-10} \ W/m^2$. The number of photons of wavelength $5.6 \times 10^{-7} \ m$ entering the eye,with a pupil area of $10^{-6} \ m^2$,per second for vision will be nearly: