The value of Planck's constant is

What should be the velocity of an electron so that its momentum becomes equal to that of a photon of wavelength $5200 \, \mathring{A}$? (Given: $h = 6.63 \times 10^{-34} \, J \cdot s$, $m_e = 9.1 \times 10^{-31} \, kg$)

An electric bulb of $100 \ W$ power emits photons of wavelength $410 \ nm$ per second. The number of photons emitted per second is: $(h = 6.63 \times 10^{-34} \ J \cdot s, c = 3 \times 10^8 \ m/s)$

The wavelength of an electron and a photon are equal. If the energy of the photon is $E$ and the momentum of the electron is $p$,what is the value of $p/E$?

Light from a source travels out with a velocity $c$. If the source moves away from the observer with a velocity $v$,then the relative velocity of light with respect to the observer is

An atom absorbs a photon of wavelength $500\,nm$ and emits another photon of wavelength $600\,nm$. The net energy absorbed by the atom in this process is $n \times 10^{-4}\,eV$. The value of $n$ is ............ [Assume the atom to be stationary during the absorption and emission process] (Take $h = 6.6 \times 10^{-34}\,Js$ and $c = 3 \times 10^8\,m/s$)