All fringes of diffraction are of-

Options

A. the same intensity
B. unequal width
C. the same width
D. full darkness

Answer

To determine the nature of the fringes in diffraction, we need to analyze the behavior of light as it passes through a single slit. Here’s a step-by-step solution to the question:

### Step 1: Understanding Diffraction
When light passes through a single slit of width \( D \), it spreads out and creates a pattern of light and dark fringes on a screen. This phenomenon is known as diffraction.

**Hint:** Remember that diffraction occurs when waves encounter an obstacle or aperture that is comparable in size to their wavelength.

### Step 2: Analyzing the Central Maximum
The central maximum is the brightest fringe and occurs directly in line with the slit. The intensity of light is highest at this point and decreases as you move away from the center.

**Hint:** The central maximum is always the brightest part of the diffraction pattern.

### Step 3: Understanding Intensity Variation
As you move away from the central maximum, the intensity of the light decreases. This means that the fringes are not of equal intensity; they get dimmer as you move away from the center.

**Hint:** The intensity of the fringes is not uniform; it decreases as you move away from the central maximum.

### Step 4: Width of the Fringes
The width of the fringes can be determined using the formula for minima in a single-slit diffraction pattern. The positions of the minima are given by:
\[ D \sin \theta = n \lambda \]
where \( n \) is the order of the minima, \( \lambda \) is the wavelength of the light, and \( D \) is the width of the slit.

**Hint:** The width of the fringes is determined by the angle \( \theta \) and the distance from the slit to the screen.

### Step 5: Approximating Small Angles
For small angles, we can use the approximation \( \sin \theta \approx \tan \theta \approx \theta \). This leads to the conclusion that the distance between consecutive minima is not constant, and thus the widths of the fringes are unequal.

**Hint:** The approximation of small angles is crucial in determining the fringe width.

### Step 6: Conclusion on Fringes
From the analysis, we conclude that all fringes of diffraction are of unequal width due to the nature of the light spreading out and the varying intensity levels.

**Hint:** Remember that the actual width of the fringes is influenced by the angle and the distance from the slit, leading to unequal widths.

### Final Answer
Thus, the correct answer is that all fringes of diffraction are of **unequal width**.