In Young.s double slit experiment both the slits are similar. If width of one of the slits is doubled then

Options

A. dark fringes become narrower
B. bright fringes become less bright
C. dark fringes become slightly brighter
D. bright fringes become narrower

Answer

To solve the problem regarding the effect of doubling the width of one slit in Young's double slit experiment, let's analyze the situation step by step.

### Step 1: Understand the Setup
In Young's double slit experiment, we have two slits that are initially identical. Each slit allows light to pass through and creates an interference pattern on a screen due to the superposition of light waves from both slits.

**Hint:** Remember that the interference pattern is formed due to the constructive and destructive interference of light waves from both slits.

### Step 2: Effect of Doubling the Width of One Slit
When the width of one slit is doubled, the amplitude of the light wave passing through that slit also increases. This is because the intensity of light is proportional to the square of the amplitude. Therefore, if the width of one slit is doubled, the amplitude of the light wave from that slit becomes greater.

**Hint:** Recall that intensity is related to the amplitude of the wave, which affects the brightness of the fringes.

### Step 3: Analyze the Interference Pattern
In the interference pattern, the bright fringes are formed by constructive interference, and the dark fringes are formed by destructive interference. When one slit has a greater amplitude, the condition for destructive interference changes.

- For dark fringes (destructive interference), the condition is that the path difference between the two waves must be an odd multiple of half the wavelength.
- If one slit has a higher amplitude, the intensity of the dark fringes will be affected, making them less dark (or slightly brighter) than before.

**Hint:** Consider how the amplitude affects the intensity of the resulting light at the points of destructive interference.

### Step 4: Conclusion
As a result of doubling the width of one slit, the dark fringes become slightly brighter because the increased amplitude from the wider slit reduces the contrast between the dark and bright fringes. Therefore, the correct answer to the question is that the dark fringes become slightly brighter.

**Hint:** Think about how changes in amplitude influence the overall brightness of the interference pattern.

### Final Answer
The dark fringes become slightly brighter.