Question

In YDSE, a white light is formed fringe pattern on the screen. Calculate the path difference of the light waves from the two slits at the center of the first bright fringe above the central maximum.

• A. 0
• B. $\frac{1}{4}\lambda$
• C. $\frac{1}{2}\lambda$
• D. $\lambda$
• E. $\frac{3}{2}\lambda$

Answer 1

The correct option is D $\lambda$

In YDSE ,for constructive interference (for bright fringes) , the path difference is given by $\Delta x=n\lambda$ where $n=0,1,2,\mathrm{3....}$ (order of bright fringe)

therefore for first fringe $n=1$

$\Delta x=\lambda$