Light of energy 2.0 eV falls on a metal of work function 1.4 eV . The stopping potential is

Options

A. 0.6 V
B. 2.0 V
C. 3.4 V
D. 1.4 V

Answer

To solve the problem, we need to find the stopping potential when light of energy 2.0 eV falls on a metal with a work function of 1.4 eV. Here’s the step-by-step solution:

### Step 1: Understand the given values
- Energy of the incident light (E) = 2.0 eV
- Work function of the metal (Φ) = 1.4 eV

### Step 2: Calculate the maximum kinetic energy (K.E.) of the emitted electrons
The maximum kinetic energy of the emitted electrons can be calculated using the photoelectric equation:
\[ K.E. = E - \Phi \]
Substituting the given values:
\[ K.E. = 2.0 \, \text{eV} - 1.4 \, \text{eV} = 0.6 \, \text{eV} \]

### Step 3: Relate maximum kinetic energy to stopping potential
The maximum kinetic energy of the electrons can also be expressed in terms of the stopping potential (V_s):
\[ K.E. = e \cdot V_s \]
where \(e\) is the charge of the electron. Since we are dealing with electron volts, we can express the kinetic energy directly in volts:
\[ 0.6 \, \text{eV} = V_s \]

### Step 4: Conclusion
Thus, the stopping potential \(V_s\) is:
\[ V_s = 0.6 \, \text{V} \]

### Final Answer
The stopping potential is **0.6 V**.

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