Which of the following is the SI unit for intensity?

• A. watt per square meter (W/m^2)
• B. candela (cd)
• C. newton (N)
• D. joule (J)

Answer: (A)

Verified step by step guidance

1. Understand that intensity in physics and chemistry typically refers to power per unit area, which measures how much energy passes through a given area per unit time.
2. Recall that power is measured in watts (W), where 1 watt equals 1 joule per second (1 W = 1 J/s).
3. Recognize that intensity is defined as power divided by area, so its unit must be power unit divided by area unit.
4. Since area is measured in square meters (m^2) in the SI system, the unit for intensity becomes watts per square meter, written as \(\mathrm{W/m^2}\).
5. Compare the given options: candela (cd) is a unit of luminous intensity (different concept), newton (N) is a unit of force, and joule (J) is a unit of energy, so the correct SI unit for intensity is watt per square meter (\(\mathrm{W/m^2}\)).