How do you calculate intensity?

How do you calculate intensity?

• A. Divide the beam's cross-sectional area by power
• B. Multiply power by area
• C. Divide the beam's power by the beam's cross-sectional area
• D. Add power and area

Answer: (C)

Intensity is the amount of power delivered per unit area. It’s defined as the beam’s power divided by the cross-sectional area over which that power is spread. So if a beam has power P and cross-sectional area A, the intensity is I = P/A, with units of watts per square meter. This reflects the idea that spreading the same power over a larger area lowers the power per unit area, while squeezing it into a smaller area raises it. For example, a 100 W beam spread over 0.5 m^2 gives 200 W/m^2. The other options don’t match this idea: multiplying power by area gives a quantity with incompatible units, adding power and area isn’t dimensionally meaningful, and taking the inverse would give area per power, not intensity.

Intensity is the amount of power delivered per unit area. It’s defined as the beam’s power divided by the cross-sectional area over which that power is spread. So if a beam has power P and cross-sectional area A, the intensity is I = P/A, with units of watts per square meter. This reflects the idea that spreading the same power over a larger area lowers the power per unit area, while squeezing it into a smaller area raises it. For example, a 100 W beam spread over 0.5 m^2 gives 200 W/m^2. The other options don’t match this idea: multiplying power by area gives a quantity with incompatible units, adding power and area isn’t dimensionally meaningful, and taking the inverse would give area per power, not intensity.