Question

In a photoelectric effect experiment a light of frequency 1.5 times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be:

• A. Doubled
• B. Quadrupled
• C. Zero
• D. Halved

Answer 1

The Correct Option is C

Given:

The scenario concerns the relationship between incident frequency \( f \) and threshold frequency \( f_0 \) for photoelectron emission. The provided inequality is \( \frac{f}{2}<f_0 \).

Step 1: Interpretation of the frequency relationship

The inequality \( \frac{f}{2}<f_0 \) signifies that the incident frequency \( f \) is less than twice the threshold frequency \( f_0 \). This implies the incident light's frequency is below the minimum requirement for photoelectron emission.

Step 2: Explanation of the photoelectric effect

Photoelectron emission occurs when light of a frequency equal to or greater than the threshold frequency \( f_0 \) strikes a material. If the incident frequency is lower than \( f_0 \), the photon energy is insufficient to eject photoelectrons.

Step 3: Deduction from the given condition

As \( f<f_0 \), the photons lack the energy to overcome the material's work function, consequently preventing photoelectron emission.

Conclusion:

Consequently, the current, which is proportional to the number of emitted photoelectrons, is zero: \[ \Rightarrow \text{current} = 0 \]

Final Answer:

No photoelectrons are emitted, resulting in no current generation.