Which of the following diagrams represent the veriation of electric field vector with time for a circularly polarised light

Options

A. (a)
B. (b)
C. (c)
D. (d)

Answer

B

Explanation

When two plane-polarised waves are superimposed, then under certain conditions, the resultant light vector rotates with a constant magnitude in a plane perpendicular to the direction of propagation. The tip of the vector traces a circle and the light is said to be circulary polarised.
To form circulary polarised that
`E_x=E_0 sin omegat`
`E_y=E_0 cos omega t=E_0sin (omegat +pi/2)`
where `E_0` is amplitude.
Resultant amplitude
`|vecE|^2=E_0+E_0+2E_0.E_0co spi/2`
`|vecE|=E_0sqrt2=const ant`
Hence, the correct graph will be (a).