The energy (E) and momentum (p) of photon are respectively, (symbols have their usual meaning)

Answer

To solve the problem regarding the energy (E) and momentum (p) of a photon, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Photon**:
- A photon is a quantum of light that exhibits both wave-like and particle-like properties. It has energy and momentum.

2. **Energy of a Photon**:
- The energy (E) of a photon can be expressed using the formula:
\[ E = \frac{hc}{\lambda} \]
where:
- \( h \) is Planck's constant (\(6.626 \times 10^{-34} \, \text{Js}\)),
- \( c \) is the speed of light in vacuum (\(3 \times 10^8 \, \text{m/s}\)),
- \( \lambda \) is the wavelength of the photon.

3. **Relating Wavelength to Frequency**:
- The speed of light can also be expressed in terms of frequency (\( \nu \)) and wavelength (\( \lambda \)):
\[ c = \lambda \nu \]
- Thus, we can rewrite the energy formula in terms of frequency:
\[ E = h\nu \]

4. **Momentum of a Photon**:
- The momentum (p) of a photon can be derived from the relationship between energy and momentum. For a photon, the momentum is given by:
\[ p = \frac{E}{c} \]
- Substituting the energy expression \( E = h\nu \) into the momentum formula gives:
\[ p = \frac{h\nu}{c} \]

5. **Final Expressions**:
- Therefore, the final expressions for the energy and momentum of a photon are:
- Energy:
\[ E = h\nu \]
- Momentum:
\[ p = \frac{h\nu}{c} \]

### Summary:
- The energy of a photon is given by \( E = h\nu \).
- The momentum of a photon is given by \( p = \frac{h\nu}{c} \).