An electromagnetic wave in vaccum has the electric and magnetic fields  and which are always perpendicular to each other. the direction of polarisation is given by  and that of wave propagation by  then

• 
• 
• 
• 

C.

During the propagation of electromagnetic waves in a medium:

• Electric energy density is equal to the magnetic energy density.

• Both electric and magnetic energy densities are zero.

• Electric energy density is double of the magnetic energy density.

• Electric energy density is half of the magnetic energy density.

The threshold frequency for a metallic surface corresponds to an energy of 6.2 eV, and the stopping potential for a radiation incident on this surface 5 V. The incident radiation lies in

• X-ray region

• ultra-violet region

• infra-red region

• visible region

B.

ultra-violet region