Question

In diffraction experiment, from a single slit, the angular width of central maximum does NOT depend upon

• A. ratio of wavelength and slit width
• B. distance of the slit from the screen
• C. wavelength of light used
• D. width of the slit

Hint:

Don't confuse "angular width" with "linear width." Linear width increases as the screen is moved further away, but angular width—the angle subtended at the slit—remains constant.

Answer 1

The Correct Option is B

Step 1: Read carefully.
In single slit diffraction we look at the bright central band. The question asks which listed quantity the angular width of this central band does NOT depend on.

Step 2: Recall the width formula.
The angular width of the central maximum is $\theta = \dfrac{2\lambda}{a}$, where $\lambda$ is the wavelength and $a$ is the slit width.

Step 3: Check wavelength.
$\lambda$ sits in the formula, so wavelength does affect the angular width.

Step 4: Check slit width.
$a$ also sits in the formula, so slit width affects it too. And the ratio $\frac{\lambda}{a}$ clearly matters.

Step 5: Check the screen distance.
The distance $D$ from slit to screen does not appear anywhere in $\theta = \frac{2\lambda}{a}$. It would change the linear width on the screen ($W = \theta D$), but not the angle itself.

Step 6: State the answer.
So the angular width does not depend on the distance of the slit from the screen, which is option (B).
\[ \boxed{\text{Independent of slit-to-screen distance}} \]