If the power is constant and the beam area increases, intensity will?

If the power is constant and the beam area increases, intensity will?

• A. Increase
• B. Decrease
• C. Remain the same
• D. Fluctuate

Answer: (B)

Intensity is the power per unit area, so with the power fixed, expanding the beam spreads the same energy over a larger surface. Since I = P/A, increasing the area lowers the intensity. For example, with 100 W of power and an initial area of 1 cm^2, the intensity is 100 W/cm^2. If the area grows to 4 cm^2 while power stays at 100 W, the intensity drops to 25 W/cm^2. Hence, intensity decreases when the beam area increases.

Intensity is the power per unit area, so with the power fixed, expanding the beam spreads the same energy over a larger surface. Since I = P/A, increasing the area lowers the intensity. For example, with 100 W of power and an initial area of 1 cm^2, the intensity is 100 W/cm^2. If the area grows to 4 cm^2 while power stays at 100 W, the intensity drops to 25 W/cm^2. Hence, intensity decreases when the beam area increases.