Question

Threshold wavelength for a photoelectric cell is \( \lambda_0 \). If the work-function of the cathode of some other cell becomes \( n \) times that of the first cell, then threshold wavelength for the other cell will be:

• A. \( \lambda_0 \)
• B. \( n \lambda_0 \)
• C. \( \lambda_0 / n \)
• D. \( \lambda_0(n - 1) \)

Hint:

Threshold wavelength is inversely proportional to the work-function.

Answer 1

The Correct Option is C

Step 1: The work-function \( W \) and threshold wavelength \( \lambda \) are related as: \[ W \propto \frac{1}{\lambda} \] Step 2: If the work-function increases \( n \) times: \[ \lambda' = \frac{\lambda_0}{n} \] \[ \boxed{\lambda_0 / n} \]