Let $n_r$ and $n_b$ be respectively the number of photons emitted by a red bulb and a blue bulb of equal power in a given time.

Energy of a photon whose frequency is $10^{12} \text{ MHz}$ is
[ Planck's constant,$h = 6.63 \times 10^{-34} \text{ Js}, e = 1.6 \times 10^{-19} \text{ C}$ ]

The principle of $LASER$ action involves:

The number of photons of wavelength $540 \ nm$ emitted per second by an electric bulb of power $100 \ W$ is (taking $h = 6 \times 10^{-34} \ J \cdot s$ and $c = 3 \times 10^8 \ m/s$):

The ratio of the power of a light source $S_1$ to that of the light source $S_2$ is $2$. $S_1$ is emitting $2 \times 10^{15}$ photons per second at $600 \ nm$. If the wavelength of the source $S_2$ is $300 \ nm$,then the number of photons per second emitted by $S_2$ is . . . . . . $\times 10^{14}$.

The fact that photons carry energy was established by