The energy of the em waves is of the order of 15 keV. To which part of the spectrum does it belong ?

A radiation of energy 'E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (C = Velocity of light)

Light with an energy flux of 25 $$ \times $$ 10⁴ W m^$$-$$2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm², the average force exerted on the surface is

An electromagnetic wave of frequency $$\upsilon = 3.0$$ MHz passes from vaccum into a dielectric medium with relative permittivity $${{\varepsilon _r}}$$ = 4.0. Then