$A$ situation of population inversion is related to

According to the corpuscular theory of light,the different colours of light are due to

Which of the following will have the least value of $\frac{q}{m}$?

The energy of a photon with a wavelength of $450 \, nm$ is ............

$A$ perfectly reflecting mirror of mass $M$ mounted on a spring constitutes a spring-mass system of angular frequency $\Omega$ such that $\frac{4 \pi M \Omega}{h} = 10^{24} \text{ m}^{-2}$,where $h$ is Planck's constant. $N$ photons of wavelength $\lambda = 8 \pi \times 10^{-6} \text{ m}$ strike the mirror simultaneously at normal incidence such that the mirror gets displaced by $1 \mu\text{m}$. If the value of $N$ is $x \times 10^{12}$,then the value of $x$ is. . . . . . . . [Consider the spring as massless]

The momentum of a photon is $3.3 \times 10^{-29} \ kg \ m/s$. Its frequency will be