Question

Graph shows the variation of fringe width ( X ) versus distance of the screen from the plane of the slits (D) in Young's double slit experiment. (keeping other parameters same, \(d=\) distance between the slits). The wavelength of light used can be calculated as

• A. slope \(\times \mathrm{d}^{2}\)
• B. \(\frac{\mathrm{d}}{\text{ slope }}\)
• C. \(\frac{\text{ slope }}{\mathrm{d}}\)
• D. slope \(\times \mathrm{d}\)

Hint:

Fringe width is proportional to D, so the slope of the graph is lambda divided by d.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
In the double slit experiment the fringe width is \(X=\dfrac{\lambda D}{d}\).

Step 2: Read the graph
The graph of \(X\) against \(D\) is a straight line through the origin, so its slope is \(\dfrac{X}{D}=\dfrac{\lambda}{d}\).

Step 3: Calculation
\(\lambda=\text{slope}\times d\).

Final Answer:
The wavelength equals the slope multiplied by d. \[ \boxed{\text{(D) }\text{slope}\times d} \]