According to Einstein's photoelectric equation (symbols have their usual meaning)

Options

A. `hv - phi = (KE)_max`
B. `hvgt(KE)_max`
C. `phi = hv+ (KE)_max/2`
D. `phi = (KE)_max- (hv)/2`

Answer

To solve the question regarding Einstein's photoelectric equation, we will follow these steps:

### Step 1: Understand the Photoelectric Effect
The photoelectric effect occurs when light (photons) hits a material and causes the ejection of electrons. The energy of the incoming photons must be greater than a certain threshold energy (Φ) for electrons to be emitted.

### Step 2: Write Down Einstein's Photoelectric Equation
Einstein's photoelectric equation can be expressed as:
\[ K.E. = h\nu - \Phi \]
where:
- \( K.E. \) is the maximum kinetic energy of the emitted electrons,
- \( h \) is Planck's constant,
- \( \nu \) is the frequency of the incident light,
- \( \Phi \) is the threshold energy of the material.

### Step 3: Analyze the Equation
From the equation, we can see that:
- If the energy of the photon (\( h\nu \)) is greater than the threshold energy (\( \Phi \)), then electrons will be emitted.
- The excess energy (the difference between \( h\nu \) and \( \Phi \)) is converted into the kinetic energy of the emitted electrons.

### Step 4: Identify the Correct Explanation
The correct explanation of Einstein's photoelectric equation is that the maximum kinetic energy of the emitted electrons is equal to the energy of the incoming photon minus the threshold energy. This means that the energy left after overcoming the threshold is what gives the electrons their kinetic energy.

### Conclusion
Thus, the correct interpretation of Einstein's photoelectric equation is:
\[ K.E. = h\nu - \Phi \]