If $h$ is Planck's constant,the momentum of a photon with a wavelength of $0.01 \ \mathring A$ is .........

The ratio of the energy of a photon with $\lambda = 150\,nm$ to that with $\lambda = 300\,nm$ is

If $n_r$ and $n_b$ are the number of photons emitted per second by a red bulb and a blue bulb of equal power respectively,then:

The energy of a photon of visible light with the maximum wavelength in $eV$ is approximately .......

The momentum of a photon with a wavelength of $5000\,\mathring{A}$ is:

Two sources of light emit $X$-rays of wavelength $1 \ nm$ and visible light of wavelength $500 \ nm$,respectively. Both sources emit light of the same power $200 \ W$. The ratio of the number of photons emitted per second by the $X$-ray source to the number of photons emitted per second by the visible light source is: