ShareForce, Energy, & Motion - Wave Amplitude
Amplitude means a measure of the amount of energy in a wave. Notice in the drawing below how the amplitude measures the height a wave is going above or below the resting position of the wave.
In a transverse wave, amplitude is the measure from the resting position to either the crest (high point of the wave) or to the trough (low point of the wave.)
In a longitudinal wave, like this video, amplitude is measured by determining how far the molecules of the medium have moved from their normal rest position. The concept of measuring how far molecules move is difficult to measure, so amplitude is usually only discussed in terms of transverse waves.
In the following examples, which has the greatest amplitude?
A
B
C
Highlight the box below to check your answer:
B |
Think of amplitude in terms of a wave on water. The bigger (taller) the wave the more the boat moves up and down because of greater amplitude! It takes energy to move a boat in the water. But you'll notice the boat stays in the same place, it only goes up and down. This is because the energy that made the wave is transferring through the water, it is not transferring the water. The water is the medium that the energy is being transferred though. The definition of a wave is transfer energy through matter or space. Smaller waves cause less movement because they have less energy - or a smaller amplitude. Larger waves like a tsunami hold a huge amount of energy. That is why they are so damaging.
Another factor of a wave is the wavelength. Wavelength is a measure of the distance between two crests or two troughs of a wave. The greater the wavelength, the more energy a wave has. "AM" radio stations have a big wavelength. You might have tuned the radio dial at night and heard stations that were far away and unable to be heard during the daytime. Similarly, an "FRS" radio is only able to transmit for a short distance because it uses a short wavelength and low power (amplitude.)
Notice in this movie how a drop of falling water has energy when it hits the pond below it. The drop's energy is transferred to the pond when it hits. As the energy is transferred to the pond, the waves move away from the drop in yet another transfer of energy. (Replay the video and watch the waves move away from the drop again.)
