A source emits 45 joules of energy in 15 s. What is the radiant flux of the source ?

Explanation

To find the radiant flux of the source, we can use the formula for radiant flux (Φ), which is defined as the total energy emitted (E) divided by the time (t) over which the energy is emitted.

### Step-by-Step Solution:

1. **Identify the given values:**
- Total energy emitted (E) = 45 joules
- Time (t) = 15 seconds

2. **Use the formula for radiant flux:**
\[ \Phi = \frac{E}{t} \]
where:
- Φ is the radiant flux,
- E is the total energy emitted,
- t is the time period.

3. **Substitute the known values into the formula:**
\[ \Phi = \frac{45 \, \text{joules}}{15 \, \text{seconds}} \]

4. **Perform the calculation:**
\[ \Phi = 3 \, \text{watts} \]

5. **Conclusion:**
The radiant flux of the source is 3 watts.