JEE PYQ: Atomic Physics Question 29
Question 29 - 2020 (03 Sep Shift 2)
Two sources of light emit X-rays of wavelength 1 nm and visible light of wavelength 500 nm, respectively. Both the sources emit light of the same power 200 W. The ratio of the number density of photons of X-rays to the number density of photons of the visible light of the given wavelengths is:
(1) $\frac{1}{500}$
(2) 250
(3) $\frac{1}{250}$
(4) 500
Show Answer
Answer: (1)
Solution
Number of photons emitted per second from a source of monochromatic radiation of wavelength $\lambda$ and power $P$ is $n = \frac{P}{E} = \frac{P}{h\nu} = \frac{P\lambda}{hc}$. Clearly $n \propto \lambda$. $\frac{n_1}{n_2} = \frac{\lambda_1}{\lambda_2} = \frac{1}{500}$.
BETA
