The rest mass of the photon is

Options

A. `(hv)/(c )`
B. `(hv)/(c^(2))`
C. `(hv)/(lamda)`
D. zero

Explanation

To solve the question regarding the rest mass of a photon, we can follow these steps:

### Step 1: Understand the Concept of Rest Mass
Rest mass refers to the mass of an object when it is at rest. It is the intrinsic mass of the object, which does not change regardless of its state of motion.

**Hint:** Remember that rest mass is measured when an object is not moving.

### Step 2: Identify the Nature of a Photon
A photon is a quantum of electromagnetic radiation. It is often described as a particle of light and is characterized by its energy and momentum. Importantly, photons always travel at the speed of light in a vacuum.

**Hint:** Consider the properties of light and how photons behave in different states.

### Step 3: Apply the Concept of Mass-Energy Equivalence
According to Einstein's theory of relativity, the relationship between mass and energy is given by the equation \(E = mc^2\). However, for massless particles like photons, this relationship takes a different form.

**Hint:** Think about how energy relates to mass for particles that travel at the speed of light.

### Step 4: Analyze the Rest Mass of a Photon
For a photon, when it is at rest (hypothetically, since photons cannot be at rest), its energy would be zero. Since the equation \(E = mc^2\) implies that if energy \(E\) is zero, then the mass \(m\) must also be zero. Therefore, the rest mass of a photon is zero.

**Hint:** Recall that photons are never at rest in reality, but theoretically, if they were, their energy would be zero.

### Step 5: Conclusion
Based on the above analysis, we conclude that the rest mass of a photon is zero.

**Final Answer:** The rest mass of the photon is \(0\).