Any point on a transverse wave moves up and down in a repeating pattern.
The shortest time that a point takes to return to the initial position (one vibration) is called period, T. In this example, every vibration is marked with a short pause.
The number of vibrations per second is called and is measured in hertz (Hz). Here's the equation for frequency:
f = 1 / T
The shortest distance between peaks, the highest points, and troughs, the lowest points, is the wavelength, .
By knowing the frequency of a wave and its wavelength, we can find its velocity. Here is the equation for the velocity of a wave:
The velocity of a wave is only affected by the properties of the medium.
It is not possible to increase the speed
of a wave by increasing its wavelength. By doing this, the number of vibrations
per second decreases and therefore the velocity remains the same.
The amplitude of a wave is the distance from a crest to where the wave is at equilibrium. The amplitude is used to measure the energy transferred by the wave. The bigger the distance, the greater the energy transferred.
Once a wave (incident wave) has reached the end of a medium, part of the energy is transferred to the medium that is immediately next to it (transmitted wave) and part is reflected backward (reflected wave).
The energy transferred depends on the difference between the mediums.
If there is a significant difference, almost all the energy will be reflected.
If the mediums are similar, most of the energy will be transferred.
However, the reflected
waves will be inverted if the medium that comes next is more dense or
it won't be inverted if the medium is less dense.
When two waves traveling in opposite
This is called interference
and there are of two types:
Constructive interference is when the amplitudes of the initial waves are in the same direction.
The resulting wave will be larger than the original waves.
Destructive interference is when the amplitudes of the initial waves are opposite.
The amplitude of the resulting wave will be zero.
of waves of two dimensions
(waves on water surface)
When a wave hits a barrier,
it will be reflected depending on the direction of the barrier (normal).
When a wave enters a different medium (more shallow region) at an angle, the direction of waves changes.
This change is called refraction.
When a wave travels through a small hole in a barrier, it bends around the edges. This is called Diffraction.
Sound waves are longitudinal
waves produced by variations in air pressure.
The energy of a sound wave
travels away from the source trough a series of molecule collisions parallel
to the direction of the wave.
Sound waves can also travel
trough liquids and solids.
Measuring sound waves
The frequency of a sound wave is called pitch. In music, different pitches
(C, D, E, etc.) are
The human ear is able to feel frequencies between 20 Hz to 15 000 Hz,
depending on the age
The amplitude or volume of a sound wave is the amount of pressure exerted
by a sound source
Scientists measure the amplitude in atmospheres. Humans can detect from
less than a billionth
The sound produced by the
source is always the same, however, John is receiving more oscillations
The sound that reaches John's
ear has a higher pitch than the sound that reaches Bob's ear.
Interference of waves
When two or more waves with the same frequency reach the ear, the ear
interprets these waves
When two waves with different frequencies reach the ear, the resulting sound will be pleasant if the frequencies have ratios that are small whole numbers (2:1, 3:2, 4:3). This is called
On the other hand, an unpleasant
sound or noise will be produced if the frequencies have ratios
other than small whole numbers.
This is called dissonance.