A parallel beam of white light is incident normally on surface which absorbs 70% of the incident light and reflects the rest. If incident beam has power of 40 W , then what will be the magnitude of force exerted by the light on this surface ?

Explanation

To solve the problem, we need to determine the force exerted by a beam of light on a surface that absorbs 70% of the incident light and reflects the remaining 30%. The power of the incident beam is given as 40 W.

### Step-by-Step Solution:

1. **Determine the Power Absorbed and Reflected:**
- The total power of the incident beam is 40 W.
- Power absorbed = 70% of 40 W = 0.70 × 40 W = 28 W.
- Power reflected = 30% of 40 W = 0.30 × 40 W = 12 W.
...