Which of the following has a mass closest in value to that of the positron? $(1\;a.m.u = 931\;MeV)$

The energy of a photon with a wavelength of $\lambda = 4000 \ \mathring{A}$ is equal to ... $eV$.

$A$ particle which has zero rest mass and non-zero energy and momentum must travel with a speed

$1 \ J$ is equal to how many electron volt?

Two monochromatic beams $A$ and $B$ of equal intensity $I$ hit a screen. The number of photons hitting the screen by beam $A$ is twice that by beam $B$. What inference can you make about their frequencies?

$A$ photon is associated with .........