NEET Physics Question - Wave Optics - Young's Double Slit Experiment

Assertion (A): If white light is used in place of monochromatic light in YDSE then central point is white. Although at other places coloured fringes will be obtained.

Reason (R): At centre path difference is zero for all wave lengths. Hence all wave will interfere constructively.

(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)

(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

(3) (A) is true but (R) is false

(4) Both (A) and (R) are false

Solution:

In Young's double slit experiment, the central point has a path difference of zero \(\Delta x = 0\) for all wavelengths \(\lambda\). The condition for constructive interference is \(\Delta x = n\lambda\). For \(n=0\), \(\Delta x = 0\) which is true for all \(\lambda\). Therefore, all colors interfere constructively at the center, resulting in a white fringe. Other fringes are colored due to dispersion. Both are true and R explains A.

Rankers Physics

White Light in YDSE – Central Fringe

Solution:

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