If a photon has velocity $c$ and frequency $\nu$,then which of the following represents its wavelength?

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

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

The energy of a photon with a wavelength of $\lambda = 4000 \ \mathring{A}$ is equal to ... $eV$.

Two sources of light emit with a power of $200 \ W$. The ratio of the number of photons of visible light emitted per second by each source having wavelengths $300 \ nm$ and $500 \ nm$ respectively,will be:

The momentum of a photon of energy $1 \, MeV$ in $kg \, m/s$ will be: