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

Light of intensity $10^{-10} \ W/m^2$ and wavelength $5.6 \times 10^{-7} \ m$ is incident on a surface of area $10^{-6} \ m^2$. What is the number of photons incident per second?

If the momentum of a photon is $p$,then its frequency is ........

$A$ radio transmitter operates at a frequency of $880 \ kHz$ and a power of $10 \ kW$. The number of photons emitted per second is .......

The value of Planck's constant is

An important spectral emission line has a wavelength of $21 \ cm$. The corresponding photon energy is $(h = 6.62 \times 10^{-34} \ J \cdot s; \ c = 3 \times 10^8 \ m/s)$.