The pressure exerted by an electromagnetic wave of intensity `I (Wm^(-2))` on a non-reflecting surface is ( c is the velocity of light)

Options

A. `Ic`
B. `Ic^(2)`
C. `I//c`
D. `I//c^(2)`

Explanation

To find the pressure exerted by an electromagnetic wave of intensity \( I \) on a non-reflecting surface, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Problem**:
We are given an electromagnetic wave with intensity \( I \) (in watts per square meter) striking a non-reflecting surface. We need to determine the pressure exerted by this wave on the surface.

2. **Concept of Pressure**:
Pressure \( P \) is defined as the force \( F \) per unit area \( A \):
\[ P = \frac{F}{A} \]

3. **Force from Momentum Change**:
The force exerted by the electromagnetic wave can be related to the change in momentum. The electromagnetic wave carries momentum, and when it strikes a surface, it transfers momentum to that surface. The force can be expressed as the rate of change of momentum:
\[ F = \frac{dP}{dt} \]

4. **Momentum Transfer**:
For a non-reflecting surface, the entire momentum of the wave is absorbed. The change in momentum \( \Delta P \) when the wave is absorbed can be related to the intensity \( I \) of the wave. The intensity \( I \) is defined as the energy per unit time per unit area:
\[ I = \frac{E}{A \cdot \Delta t} \]
where \( E \) is the energy.

5. **Relating Energy to Momentum**:
The momentum \( P \) of the electromagnetic wave can be related to its energy \( E \) by the equation:
\[ P = \frac{E}{c} \]
where \( c \) is the speed of light.

6. **Calculating Pressure**:
Since the force is the rate of change of momentum, we can substitute the expression for momentum into the force equation:
\[ F = \frac{d}{dt}\left(\frac{E}{c}\right) = \frac{1}{c} \frac{dE}{dt} \]
The term \( \frac{dE}{dt} \) is the power, which is equal to the intensity \( I \) multiplied by the area \( A \):
\[ \frac{dE}{dt} = I \cdot A \]
Thus, we can rewrite the force as:
\[ F = \frac{I \cdot A}{c} \]

7. **Substituting Back into Pressure Equation**:
Now substituting \( F \) back into the pressure equation:
\[ P = \frac{F}{A} = \frac{I \cdot A / c}{A} = \frac{I}{c} \]

8. **Final Result**:
Therefore, the pressure exerted by the electromagnetic wave on a non-reflecting surface is given by:
\[ P = \frac{I}{c} \]

### Summary:
The pressure exerted by an electromagnetic wave of intensity \( I \) on a non-reflecting surface is \( \frac{I}{c} \), where \( c \) is the speed of light.