What is the energy of a photon whose wavelength is $6840\,\mathring{A}$? (in $eV$)

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

What is the unit of energy in atomic and nuclear physics? Define it.

How many photons are emitted by a laser source of $5 \times 10^{-3} \,W$ operating at $632.2 \,nm$ in $2 \,s$? The answer is $....... \times 10^{16}$. (Given: $h = 6.63 \times 10^{-34} \,Js$,$c = 3 \times 10^8 \,m/s$)

If the energy of a photon is $10\,eV$,then its momentum is

$A$ Laser light of wavelength $660\,nm$ is used to weld Retina detachment. If a Laser pulse of width $60\,ms$ and power $0.5\,kW$ is used,the approximate number of photons in the pulse are: [Take Planck's constant $h = 6.62 \times 10^{-34}\,Js$]