If beam area doubles while power remains constant, what happens to intensity?

If beam area doubles while power remains constant, what happens to intensity?

• A. Halves
• B. Doubles
• C. Stays the same
• D. Quadruples

Answer: (A)

Intensity is the power delivered per unit area. When the beam’s area doubles but the power stays the same, the same amount of energy must be spread over twice as much surface, so the energy per unit area drops by a factor of two. In equation form, I = P/A, so doubling A with P constant makes I half as large. This helps you picture it: a beam that fans out wider delivers less power to each square meter, so it looks dimmer. The other possibilities would require the power to change or the area to scale differently, which isn’t the case here.

Intensity is the power delivered per unit area. When the beam’s area doubles but the power stays the same, the same amount of energy must be spread over twice as much surface, so the energy per unit area drops by a factor of two. In equation form, I = P/A, so doubling A with P constant makes I half as large. This helps you picture it: a beam that fans out wider delivers less power to each square meter, so it looks dimmer. The other possibilities would require the power to change or the area to scale differently, which isn’t the case here.