When light is described as an electromagnetic wave, it consists of a periodically varying electric E and magnetic field H which are oriented at an angle?

Optoelectronics and Optical Communication 

When light is described as an electromagnetic wave, it consists of a periodically varying electric E and magnetic field H which are oriented at an angle?

a) 90 degree to each other 
b) Less than 90 degree 
c) Greater than 90 degree 
d) 180 degree apart

Answer : - 90 degree to each other