Question

In Young's double slit experiment, the interference pattern is found to have an intensity ratio between bright and dark fringes is 9. This implies the

• A. the intensities at the screen due to the two slits are 5 units and 4 units respectively
• B. the intensities at the screen due to the two slits are 4 units and 1 unit respectively
• C. the amplitude ratio is 7
• D. the amplitude ratio is 6

Hint:

In Young's experiment, the intensity ratio is the square of the amplitude ratio.

Answer 1

The Correct Option is B

Step 1: Intensity and amplitude relationship.
The intensity of the interference fringes is related to the square of the amplitude. The intensity ratio between bright and dark fringes is \( 9 \), which means the amplitude ratio is \( \sqrt{9} = 3 \). Thus, the amplitude of the first slit is 3 times that of the second slit.

Step 2: Conclusion.
This implies that the intensity ratio of the two slits is 4:1. Therefore, the correct answer is option (B).

Final Answer: \[ \boxed{\text{(B) the intensities at the screen due to the two slits are 4 units and 1 unit respectively}} \]