Two sources of light emit with a power of $200 \mathrm{~W}$. The ratio of number of photons of visible light emitted by each source having wavelengths $300\ \mathrm{nm}$ and $500 \mathrm{~nm}$ respectively, will be :
$1: 5$
$1: 3$
$5: 3$
$3: 5$
A pulse of light of duration $100 \ ns$ is absorbed completely by a small object initially at rest. Power of the pulse is $30 \ mV$ and the speed of light is $3 \times 10 ^8\ ms ^{-1}$. The final momentum of the object is :
If the two metals $A$ and $B$ are exposed to radiation of wavelength $350\,nm$. The work functions of metals $A$ and $B$ are $4.8\,eV$ and $2.2\,eV$. Then choose the correct option
The energy of a photon is $E = hv$ and the momentum of photon $p = \frac{h}{\lambda }$, then the velocity of photon will be
According to photon theory of light which of the following physical quantities associated with a photon do not/does not change as it collides with an electron in vacuum