Which of the following does not characterise $X$-rays?

The wavelength of photon $A$ is $400 \ nm$. The frequency of photon $B$ is $10^{16} \ s^{-1}$. The wave number of photon $C$ is $10^{4} \ cm^{-1}$. The correct order of energy of these photons is:

What is the photoelectric effect? Explain it.

$A$ particular station of All India Radio,New Delhi,broadcasts on a frequency of $1,368 \, kHz$. The wavelength of the electromagnetic radiation emitted by the transmitter is : [speed of light $c = 3.0 \times 10^{8} \, m \, s^{-1}$]

The periodic time of radiation is $4 \times 10^{-10} \ s$. Find the wavelength,wave number,and frequency.

Work functions of four metals $M_1, M_2, M_3$ and $M_4$ are $4.8, 4.3, 4.75$ and $3.75 \ eV$ respectively. The metals which do not show photoelectric effect when light of wavelength $310 \ nm$ falls on the metals are