Question

For obtaining maximum contrast between the bright and dark fringes in an interference pattern, the intensities of the two light coherent sources should be

• A. large
• B. small
• C. equal
• D. in the ratio \(2:1\)

Hint:

Width of the central maximum is 2 lambda D over a.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
In single slit diffraction, the width of the central maximum is \(\frac{2\lambda D}{a}\).

Step 2: Equate to the slit width:
\[ \frac{2\lambda D}{a} = a \Rightarrow D = \frac{a^2}{2\lambda} \]
This is option (D). Option (B), \(\frac{a^2}{\lambda}\), would come from using only the half width of the central maximum.

Final Answer:
The distance is \(D = \frac{a^2}{2\lambda}\), option (D). \[ \boxed{D = \frac{a^2}{2\lambda}} \]