Electromagnetic Spectrum

Name the rays or waves  of highest frequency .

Give a reason for the following:

It is necessary to use satellites for long-distance TV transmission. Why?

The electric current in an X-ray tube (from the target to the filament) operating at 40 kV is 10 mA. Assume that on an average, 1% of the total kinetic energy of the electron hitting hte target are converted into X-rays.
(a) What is the total power emitted as X-rays and (b) how much heat is produced in the target every second?

Name one radiation having the wavelength longer than the wavelength of these radiations.

In an atom X, electrons absorb the energy from an external source. This energy “excites” the electrons from a lower-energy level to a higher-energy level around the nucleus of the atom. When electrons return to the ground state, they emit photons.

The figure below is the energy level diagram of atom X with three energy levels, E₁ = 0.00eV, E₂ = 1.78eV and E₃ = 2.95eV. The ground state is considered 0 eV for reference. The transition of electrons takes place between levels E₁ and E₂.

1. What wavelength of radiation is needed to excite the atom to energy level E₂ from E₁?
2. Suppose the external source has a power of 100 W. What would be the rate of photon emission?

Give one use of gamma rays.

An e.m. wave exerts pressure on the surface on which it is incident. Justify.

To which regions of the electromagnetic spectrum do the following wavelengths belong: 
(a) 250 nm 
(b) 1500 nm