Wave Intensity

Progressive waves transfer:

Energy

The intensity of a wave is the:

Amount of energy passing through a unit area per unit time

Intensity of a wave is defined as:

Power per unit area

Equation for intensity:

I=P/A, where I is intensity in W/m², P is power in W, and A is area in m²

The area the wave passes through is perpendicular to the:

Direction of its velocity

The intensity of a progressive wave is proportional to:

Amplitude squared and frequency squared

If the frequency of a wave is doubled, the intensity:

Increases by a factor of 4 (2²)

If the amplitude of a wave is doubled, the intensity:

Increases by a factor of 4 (2²)

A spherical wave is a:

Wave from a point source which spreads out equally in all directions

The area that a spherical wave passes through is the:

Surface area of the sphere

The surface area of a sphere is:

4 pi r²

As spherical waves travel further from the source, the energy it carries passes through:

Increasingly larger areas

Draw a diagram of spherical waves:

Equation for intensity at surface of sphere from which a spherical wave spreads out from:

I=P/(4 pi r²)

As energy from spherical waves moves by a factor of a times the distance away from the source, the intensity is:

1/a² of the initial intensity

Why is the intensity of spherical waves 1/a² of the initial intensity when the wave is a times the distance from the source?

Because I=P/ (4 pi r²), so if radius is increased by factor of a, intensity is increased by factor of 1/a²

Intensity of spherical waves is proportional to:

Amplitude squared

The intensity of a spherical wave decreases with:

Increasing distance from source