Introduction to Waves

Foundational concepts of wave physics including wave components, mechanical versus electromagnetic waves, types of wave motion, and basic wave calculations.

How is a wave defined in physics?

A periodic vibration in both space and time that extends from one place to another.

What does the term periodic mean when describing waves?

It means that the wave repeats.

What is a mechanical wave, and what is a primary example of one?

A wave made up of vibrations through a material medium (solid, liquid, or gas); sound is an example.

What is an electromagnetic wave, and what characterizes its movement through space?

A wave made up of vibrations of electric and magnetic fields; light is an example and it needs no material medium to move.

What is Amplitude and how is it measured?

The distance from the midpoint to the crest or trough, representing the maximum displacement from equilibrium; it is measured in meters ($m$).

How is Wavelength defined?

The distance from the top of one crest to the top of the next crest, or the distance from any one point on a wave to the next identical part.

What is Frequency and what is its standard unit of measurement?

The number of vibrations per second; measured in Hertz ($Hz$) or $1/s$.

What is the Period of a wave?

The time required for one complete vibration, measured in seconds ($s$).

What characterizes Wave Motion in terms of energy transfer?

Energy is transferred from a source to a receiver without the transfer of matter between the two points.

What defines a Transverse wave?

A wave where the direction of motion of the medium is transverse ($90^\circ$) to the direction the wave travels.

What defines a Longitudinal wave?

A wave where the direction of motion of the medium is in the same direction (longitudinal) to the direction the wave travels.

What are the mathematical formulas relating frequency ($f$) and period ($T$)?

$f = \frac{1}{T}$ and $T = \frac{1}{f}$.

How is Wave speed calculated using wavelength and period?

$$\text{Wave speed} = \frac{\text{wavelength}}{\text{period}}$$

If an electric toothbrush completes $90$ cycles every second, what are its frequency and period?

Frequency is $90\,Hz$; Period is $\frac{1}{90}\,s$.

If the Willis Tower in Chicago completes a cycle in $10\,s$, what are its frequency and period?

Frequency is $\frac{1}{10\,s} = 0.1\,Hz$; Period is $10\,s$.

If a train of freight cars (each $10\,m$ long) rolls by at a rate of three cars each second, what is the speed of the train?

$30\,m/s$.

For a water wave oscillating $3$ times each second with $2\,m$ between crests, what are the frequency, wavelength, and speed?

Frequency is $3\,Hz$, Wavelength is $2\,m$, and Wave speed is $6\,m/s$.