Out of the radiations falling on surface of a body, 30% radiations are absorebed and 30% are transmitted then its reflection coefficient will be –

Options

A. 0.3
B. 0.6
C. 0.4
D. Zero

Answer

To solve the problem, we need to determine the reflection coefficient of a body when we know the percentage of radiation that is absorbed and transmitted.

### Step-by-Step Solution:

1. **Understanding the Problem**:
We are given that:
- 30% of the radiation is absorbed (A = 0.3)
- 30% of the radiation is transmitted (T = 0.3)
We need to find the reflection coefficient (R).

2. **Using the Energy Conservation Principle**:
According to the principle of conservation of energy, the total incident radiation (Q) on the body can be expressed as the sum of the absorbed (QA), transmitted (QT), and reflected (QR) radiation:
\[ Q = QR + QA + QT \]

3. **Expressing in Terms of Coefficients**:
If we divide the entire equation by Q, we get:
\[ 1 = \frac{QR}{Q} + \frac{QA}{Q} + \frac{QT}{Q} \]
Here, we can denote:
- \( R = \frac{QR}{Q} \) (reflection coefficient)
- \( A = \frac{QA}{Q} \) (absorption coefficient)
- \( T = \frac{QT}{Q} \) (transmission coefficient)

Thus, we can rewrite the equation as:
\[ 1 = R + A + T \]

4. **Substituting Known Values**:
We know:
- \( A = 0.3 \)
- \( T = 0.3 \)

Substituting these values into the equation:
\[ 1 = R + 0.3 + 0.3 \]

5. **Solving for R**:
Simplifying the equation:
\[ 1 = R + 0.6 \]
To find R, we subtract 0.6 from both sides:
\[ R = 1 - 0.6 \]
\[ R = 0.4 \]

6. **Conclusion**:
The reflection coefficient \( R \) is 0.4, meaning 40% of the incident radiation is reflected.

### Final Answer:
The reflection coefficient is **0.4**.

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