Question

Light from two coherent source of the same amplitude A and wavelength $\lambda$ illuminates the screen . The intensity of the central maximum is $I_{0}$ if the source were incoherent , the intensity at the same point will be :

• A. $4/1_{0}$
• B. $2/0$
• C. I
• D. $I_{0/2}$

Answer 1

Answer: (D)

$I_{0/2}$

Answer 2

: If source are coherent

$I_{R} = I_{1} + I_{2} + 2\sqrt{I_{1}I_{2}}\cos\varphi$

$I_{0} = I + I + 2I\cos 0{^\circ} = 4I$

If sources are incoherent,

$I_{R} = I_{1} + I_{2} = 2I = \frac{4I}{2} = \frac{I_{0}}{2}$