Average force exerted on a non-reflecting surface at normal incidence is $2.4 \times 10^{-4} \mathrm{~N}$. If $360 \mathrm{~W} / \mathrm{cm}^2$ is the light energy flux during span of $1$ hour $30$ minutes. Then the area of the surface is:

In an accelerator experiment on high-energy collisions of electrons with positrons, a certain event is interpreted as annihilation of an electron-positron pair of total energy $10.2\; BeV$ into two $\gamma$ -rays of equal energy. What is the wavelength associated with each $\gamma$ -ray? $\left(1\; BeV =10^{9}\; eV \right)$

An important spectral emission line has a wavelength of $21 cm$. The corresponding photon energy is

$(h = 6.62 \times {10^{ - 34}}Js;\;\;c = 3 \times {10^8}m/s)$

The electrons are emitted in the photoelectric effect from a metal surface

A photon of $1.7 \times {10^{ - 13}}$ Joules is absorbed by a material under special circumstances. The correct statement is

Using the Heisenberg uncertainty principle, arrange the following particles in the order of increasing lowest energy possible.

$(I)$ An electron in $H _{2}$ molecule

$(II)$ A hydrogen atom in a $H _{2}$ molecule

$(III)$ A proton in the carbon nucleus

$(IV)$ $A H _{2}$ molecule within a nanotube