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

The condition under which a microwave oven heats up a food item containing water molecules most efficiently is

The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagatting in vacuum is equal to