Question

If the wavelength is brought down from 6000 Å to 4000 Å in a photoelectric experiment then what will happen?

• A. The work function of the metal will increase
• B. The threshold frequency will decrease
• C. No change will take place
• D. Cut off voltage will increase

Hint:

Reducing the wavelength of light increases its frequency, thus increasing the energy of the photons, which results in an increased cut-off voltage.

Answer 1

The Correct Option is D

Step 1: Understanding the Effect of Wavelength.
According to the photoelectric equation: \[ E = h f \] where \(E\) is the energy of the photons and \(f\) is the frequency. Reducing the wavelength increases the frequency and thus increases the energy of the incoming photons.
Step 2: Conclusion.
As energy increases, the cut-off voltage (the minimum stopping potential) required to stop the emitted electrons will increase.
Step 3: Conclusion.
The correct answer is (D), Cut off voltage will increase.