At the given point of time, the earth receives energy from sun at 4 cal cm^–2min^–1. Determine the number of photons received on the surface of the Earth per cm² per minute. (Given: Mean wavelength of sun light = 5500 Å )

Calculate the de Broglie wavelength of a proton whose kinetic energy is equal to 81.9 x 10^–15 J. (Given: mass of proton is 1836 times that of electron).

The ratio between the de Broglie wavelength associated with proton, accelerated through a potential of 512 V and that of alpha particle accelerated through a potential of X volts is found to be one. Find the value of X.

Find the de Broglie wavelength associated with an alpha particle which is accelerated through a potential difference of 400 V. Given that the mass of the proton is 1.67 x 10^–27 kg.

Calculate the cut-off wavelength and cutoff frequency of x-rays from an x-ray tube of accelerating potential 20,000 V.