Einstein's photoelectric equation states that `E_(k) = h v - W` . In this equation `E_(k)` refers to

Options

A. Kinetic energy of all ejected electrons
B. Mean kinetic energy of emitted electrons
C. Minimum kinetic energy of emitted electrons
D. Maximum kinetic energy of emitted electrons

Explanation

To solve the question regarding Einstein's photoelectric equation, we need to identify what \( E_k \) refers to in the equation \( E_k = h\nu - W \).

### Step-by-Step Solution:

1. **Understanding the Photoelectric Effect**:
- The photoelectric effect occurs when light (radiation) of a certain frequency strikes the surface of a metal and causes the ejection of electrons from that surface.

2. **Identifying the Components of the Equation**:
- In the equation \( E_k = h\nu - W \):
- \( E_k \) represents the kinetic energy of the emitted electrons.
- \( h \) is Planck's constant.
- \( \nu \) (or \( \mu \)) is the frequency of the incident light.
- \( W \) is the work function of the metal, which is the minimum energy required to remove an electron from the surface of the metal.

3. **Relating Energy to Kinetic Energy**:
- When light of frequency \( \nu \) strikes the metal surface, if the energy \( h\nu \) of the incoming photons is greater than the work function \( W \), electrons are ejected.
- The difference between the energy of the incoming photon \( h\nu \) and the work function \( W \) gives the kinetic energy \( E_k \) of the emitted electrons.

4. **Conclusion**:
- Therefore, \( E_k \) refers to the maximum kinetic energy of the emitted electrons when the incident light has a frequency greater than the threshold frequency.

### Final Answer:
In Einstein's photoelectric equation \( E_k = h\nu - W \), \( E_k \) refers to the **maximum kinetic energy of the emitted electrons**.

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