Question

What is the SI unit of intensity ?

Answer 1

Hint: Giuseppe Mercalli, an Italian scientist, introduced a scale in 1902 that measures the intensity of an earthquake based on its effects on people and structures. His scale, in a modified form, is still in use today.

Complete answer:
In physics, radiant energy intensity is defined as the power transferred per unit area, where the area is measured on a plane perpendicular to the energy's propagation direction. It is measured in watts per square meter in the SI system.

Intensity is most commonly used with waves like acoustic waves (sound) or electromagnetic waves like light or radio waves, where the average power transfer over one period of the wave is used. Intensity can also be applied to other situations in which energy is transferred.For example, the intensity of the kinetic energy carried by drops of water from a garden sprinkler.

The term "intensity" is not synonymous with "strength," "amplitude," "magnitude," or "level," as it is sometimes used colloquially. Intensity can be calculated by multiplying the energy density (energy per unit volume) at a given point in space by the velocity at which the energy is moving. The resulting vector has power units divided by area (i.e., surface power density).

Hence, the SI unit of intensity is watts per square meter.

Note: The decibel is the unit of sound intensity. The intensity of sound is defined as the sound power per unit area. A decibel is a ratio of the observed amplitude or intensity level to a reference, which is equal to 0 dB.