The blue colour of water in the sea is due to

Work function $(W_0)$ values of six metals (in $eV$) are given below: $Li: 2.42, Mg: 3.7, Cu: 4.8, Ag: 4.3, K: 2.25, Na: 2.3$. How many of the above metals do not eject the electrons when they are made to strike with radiation of wavelength $400 \text{ nm}$? $(h = 6.62 \times 10^{-34} \text{ Js})$

State the characteristics and uses of $X$-rays.

Find the mass of a photon emitted by a sodium lamp (wavelength $\lambda = 5890 \ \mathring{A}$). How many times is this mass compared to the mass of an electron?

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength $6800 \, \mathring{A}$. Calculate threshold frequency $(v_{0})$ and work function $(W_{0})$ of the metal.

Which of the following statements is $NOT$ true?