Assertion: The specific charge of positive rays is not constant.
Reason: The mass of ions varies with speed.

By a suitable example,show that the particle or wave nature of light depends on the type of experiment.

Which of the following support the quantum nature of the $EM$ radiations?
$(A)$ Photoelectric effect
$(B)$ Compton effect
$(C)$ Doppler effect
$(D)$ Field effect

In an experiment on the photoelectric effect,plates of three different metals $p, q,$ and $r$ are used,with work functions $\phi_p = 2.0\ eV$,$\phi_q = 2.5\ eV$,and $\phi_r = 3.0\ eV$,respectively. Three radiations of equal intensity with wavelengths $550\ nm, 450\ nm,$ and $350\ nm$ are incident on these plates. Which of the following $I \rightarrow V$ graphs is correct for the experimental results? $(hc = 1240\ eV\ nm)$

Find the number of photons emitted per second from a source of light which results in a photocurrent with drift velocity of $1.5 \ m/s$ in a conductor with cross-section area $0.25 \ m^2$ and volume density of electrons $10^{20} \ m^{-3}$. (Assume that $60\%$ of photons emitted result in electron emission).

The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current $I$ of the photocell varies as follows: