Light of intensity $10^{-10} \ W/m^2$ and wavelength $5.6 \times 10^{-7} \ m$ is incident on a surface of area $10^{-6} \ m^2$. What is the number of photons incident per second?

$A$ 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 value of Planck's constant is

The rest mass of the photon is

If the energy of a photon corresponding to a wavelength of $6000 \mathring A$ is $3.32 \times 10^{-19} \ J$,the photon energy for a wavelength of $4000 \mathring A$ will be ............ $eV$.

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