Q 12-11-052JEE MainJEE Main 2025 (24 Jan, Shift 2)Easy
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 $2\times10^{15}$ photons per second at $600\ \text{nm}$. If the wavelength of the source $S_2$ is $300\ \text{nm}$, then the number of photons per second emitted by $S_2$ is ______ $\times10^{14}$.
Numerical value type. Enter your answer.
Answer: 5
Power $P = n\dfrac{hc}{\lambda}$, where $n$ is photons per second.
$$\frac{P_1}{P_2} = \frac{n_1/\lambda_1}{n_2/\lambda_2} = \frac{n_1\lambda_2}{n_2\lambda_1} = 2$$
$$n_2 = \frac{n_1\lambda_2}{2\lambda_1} = \frac{2\times10^{15}\times300}{2\times600} = 5\times10^{14}$$
Solution by Sreeraj P, M.Sc Physics