In photoelectric effect the work function of a metal is 3.5 eV. The emitted electrons can be stopped by applying a potential of –1.2 V. Then

Options

A. the energy of the incident photons is `4.7eV`
B. the energy of the incident photons is `2.3eV`
C. if higher frequency photons be used , the photoelectric current will rise
D. when the energy of photons is `3.5eV` , the photoelectric current will be maximum

Answer

To solve the problem regarding the photoelectric effect, we will follow these steps:

### Step 1: Understand the Given Values
We are given:
- Work function (φ) of the metal = 3.5 eV
- Stopping potential (V) = -1.2 V

### Step 2: Use the Stopping Potential Formula
The stopping potential formula relates the stopping potential, the work function, and the energy of the incident photons. The formula is:
\[ eV = E - \phi \]
Where:
- \( e \) is the charge of an electron (which will cancel out),
- \( V \) is the stopping potential,
- \( E \) is the energy of the incident photons,
- \( \phi \) is the work function.

### Step 3: Rearrange the Formula
Rearranging the formula to solve for the energy \( E \):
\[ E = eV + \phi \]

### Step 4: Substitute the Known Values
Substituting the known values into the equation:
\[ E = (-1.2 \, \text{V}) + (3.5 \, \text{eV}) \]
\[ E = -1.2 + 3.5 \]
\[ E = 2.3 \, \text{eV} \]

### Step 5: Analyze the Results
The energy of the incident photons is 2.3 eV. Since this energy is less than the work function (3.5 eV), it indicates that the photons do not have enough energy to emit electrons from the metal surface.

### Step 6: Conclusion
- The emitted electrons can be stopped by applying a potential of -1.2 V, indicating that the energy of the incident photons is indeed less than the work function, confirming that no electrons will be emitted.