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

Options

A. (a)0.6 V
B. (b)2.0 V
C. (c)3.4 V
D. (d)1.4 V

Answer

To find the stopping potential when light of energy 2.0 eV falls on a metal with a work function of 1.4 eV, we can follow these steps:

### Step 1: Understand the Photoelectric Effect
The photoelectric effect describes how electrons are emitted from a metal surface when it is exposed to light (or electromagnetic radiation) of sufficient energy. The energy of the incident light must overcome the work function of the metal to release electrons.

### Step 2: Identify Given Values
- Energy of incident light (E) = 2.0 eV
- Work function of the metal (Φ) = 1.4 eV

### Step 3: Calculate Maximum Kinetic Energy (K.E. max)
Using the photoelectric equation:
\[ \text{K.E.}_{\text{max}} = E - \Phi \]
Substituting the values:
\[ \text{K.E.}_{\text{max}} = 2.0 \, \text{eV} - 1.4 \, \text{eV} = 0.6 \, \text{eV} \]

### Step 4: Relate Kinetic Energy to Stopping Potential
The maximum kinetic energy of the emitted electrons is also related to the stopping potential (V_s) by the equation:
\[ \text{K.E.}_{\text{max}} = e \cdot V_s \]
Where \( e \) is the charge of the electron (which is a constant and cancels out when we express energy in eV).

### Step 5: Solve for Stopping Potential
Since we have already calculated the maximum kinetic energy:
\[ 0.6 \, \text{eV} = e \cdot V_s \]
Thus, we can directly equate:
\[ V_s = 0.6 \, \text{V} \]

### Final Answer
The stopping potential \( V_s \) is **0.6 V**.

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