If $p$ is the momentum of the fastest electron ejected from a metal surface after the irradiation of light having wavelength $\lambda$,then for $1.5 \ p$ momentum of the photoelectron,the wavelength of the light should be: (Assume kinetic energy of ejected photoelectron to be very high in comparison to work function)

Explain the properties of electromagnetic waves.

What is the wavelength for a wave having frequency $50 \ Hz$?

The region in the electromagnetic spectrum where the Balmer series lines appear is

Identify the region of the electromagnetic spectrum for the spectral lines when electron transition takes place from higher energy levels to $n=3, 4, 5$ in the atomic spectrum of hydrogen.

Which of the following statements is correct about the photoelectric effect?
$1$. The number of electrons ejected from a metal surface is inversely proportional to the intensity of light.
$2$. Below the threshold frequency,the photoelectric effect can be observed.
$3$. At a frequency higher than the threshold frequency,the ejected electrons have a certain kinetic energy.
$4$. At a frequency higher than the threshold frequency,the electron is still on the metal surface.