In Young's double slit experiment, the two slits acts as coherent sources of equal amplitude A and wavelength `lambda`. In another experiment with the same set up the two slits are of equal amplitude A and wavelength `lambda` but are incoherent. The ratio of the intensity of light at the mid-point of the screen in the first case to that in the second case is

Options

A. `4:1`
B. `1:1`
C. `2:1`
D. `1:4`

Answer

C

Explanation

Intesity in the first case, `I_(1)=4I_(0)`
where, `I_(0)` = intensity due to each source
Intensity in second case, `I_(2)=2I_(0)`
`:. I_(1)/I_(2)=(4I_(0))/(2I_(0))=2/1`