The diffraction pattern due to a straight edge contains

Options

A. alternate bright and dark bands of same width
B. alternate bright and dark bands with decreasing width as the order of the band increases in the illuminated part
C. alternate bright and dark bands with increasing width as the order of the band increases
D. none of the above is true

Answer

To solve the question regarding the diffraction pattern due to a straight edge, we can follow these steps:

### Step 1: Understand Diffraction
Diffraction is the bending of waves around obstacles or through openings. When waves encounter a straight edge, they spread out and create a pattern of alternating light and dark regions.

**Hint:** Recall the definition of diffraction and how it relates to wave behavior around edges.

### Step 2: Visualize the Setup
Imagine a wave source emitting waves that encounter a straight edge. The waves will bend around the edge and produce a pattern on a screen placed behind the edge.

**Hint:** Draw a diagram showing the wavefronts approaching the straight edge and how they diffract around it.

### Step 3: Analyze the Diffraction Pattern
The diffraction pattern created by a straight edge consists of alternating bright and dark bands. The key characteristic of this pattern is that the width of these bands changes as you move further from the edge.

**Hint:** Think about how the intensity of the light changes and how the spacing of the bands might vary.

### Step 4: Determine Band Width Behavior
As you move away from the edge, the width of the bright and dark bands decreases. This means that the first few bands are wider, and as you go to higher orders, the bands become narrower.

**Hint:** Consider how the geometry of the wavefronts changes with distance from the edge.

### Step 5: Choose the Correct Option
Given the options:
- Alternate bright and dark bands of the same width
- Alternate bright and dark bands with decreasing width as the order of the band increases
- Alternate bright and dark bands with increasing width as the order of the band increases
- None of the above

The correct answer is that the diffraction pattern contains alternate bright and dark bands with decreasing width as the order of the band increases.

**Hint:** Review the options carefully and match them with your understanding of the diffraction pattern.

### Final Answer
The diffraction pattern due to a straight edge contains alternate bright and dark bands with decreasing width as the order of the band increases. Therefore, the answer is option B.

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