Question

In an experiment on Newton's rings, the diameter of the 20th dark ring was found to be 5.82mm and that of the 10th dark ring was 3.16mm. The wavelength of light used is:

• A. 5646Å
• B. 8969Å
• C. 5406Å
• D. 5900Å

Hint:

The formula for Newton's rings involves the square root of the product of the ring number, wavelength, and the radius of curvature.

Answer 1

The Correct Option is A

Step 1: Use the formula for Newton's rings. The diameter of the \( n \)-th dark ring is given by: \[ D_n = \sqrt{n \lambda R} \] Where \( n \) is the ring number, \( \lambda \) is the wavelength of light, and \( R \) is the radius of curvature.
Step 2: Conclusion. By using the values for the diameters and solving for \( \lambda \), we find that the wavelength is 5646Å.