Given that p joule of heat is incident on a body and out of it q joule is reflected and transmitted by it. The absorption co-efficient of the body is :

Options

A. `p//q`
B. `q//p`
C. `(q-p)//p`
D. `(p-q)//p`

Explanation

To find the absorption coefficient of a body when a certain amount of heat is incident upon it, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Values**:
- Let \( P \) be the total heat incident on the body (in joules).
- Let \( Q \) be the total heat that is reflected and transmitted by the body (in joules).

2. **Understand the Heat Transfer Relation**:
- The heat incident on the body can be expressed as the sum of the heat absorbed (\( A \)), reflected (\( R \)), and transmitted (\( T \)):
\[ P = A + R + T \]
- Since \( Q \) is the heat that is reflected and transmitted, we can write:
\[ Q = R + T \]

3. **Express the Heat Absorbed**:
- From the above equations, we can express the heat absorbed (\( A \)) as:
\[ A = P - Q \]

4. **Define the Absorption Coefficient**:
- The absorption coefficient (\( \alpha \)) is defined as the ratio of the heat absorbed to the heat incident:
\[ \alpha = \frac{A}{P} \]

5. **Substitute the Expression for Absorbed Heat**:
- Now, substitute \( A \) from step 3 into the absorption coefficient formula:
\[ \alpha = \frac{P - Q}{P} \]

6. **Final Expression**:
- Thus, the absorption coefficient of the body can be expressed as:
\[ \alpha = \frac{P - Q}{P} \]

### Conclusion:
The absorption coefficient of the body is given by:
\[ \alpha = \frac{P - Q}{P} \]