Wave properties

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

For teachers: ready-to-use lesson slides, revision notes, diagrams for Wave properties (NGSS Middle School Science, Physics) — use them in your lesson, or run the topic as an interactive class activity your students play as a live game.

Lesson notes

What is a Wave?

A wave is a **disturbance** that transfers **energy** from one place to another without transferring matter.
Waves are caused by a vibration or oscillation that travels through a medium (or space).
The **medium** is the material through which a wave travels (e.g., air, water, solid).
In a wave, particles of the medium oscillate around an **equilibrium position**; they do not travel with the wave.

Wave Properties: Amplitude, Wavelength, Frequency

**Amplitude** is the maximum displacement of a point on the wave from its equilibrium position. It relates to the **energy** carried by the wave (higher amplitude = more energy).
**Wavelength** (λ) is the distance between two consecutive corresponding points on the wave (e.g., crest to crest).
**Frequency** (f) is the number of complete waves that pass a point per second, measured in **hertz (Hz)**.
Wave speed (v) = frequency × wavelength (v = fλ).

Transverse Waves

In a **transverse wave**, the particles of the medium vibrate **perpendicular** to the direction of wave travel.
Examples: light waves (electromagnetic), waves on a string, water waves (surface).
Transverse waves have **crests** (high points) and **troughs** (low points).

Longitudinal Waves

In a **longitudinal wave**, the particles of the medium vibrate **parallel** to the direction of wave travel.
Examples: sound waves in air, seismic P-waves.
Longitudinal waves consist of **compressions** (regions where particles are close together) and **rarefactions** (regions where particles are spread apart).

Energy Carried by Waves

Waves transfer **energy** from one location to another without transferring matter.
The energy carried by a wave depends on its **amplitude**: larger amplitude means more energy.
For mechanical waves, energy also depends on the medium's properties (e.g., density).
Electromagnetic waves (like light) carry energy through empty space.

Wave Behavior: Reflection and Refraction

**Reflection** occurs when a wave bounces off a surface; the angle of incidence equals the angle of reflection.
**Refraction** is the bending of a wave as it passes from one medium to another, due to a change in wave speed.
When a wave enters a denser medium, it slows down and bends toward the normal; in a less dense medium, it speeds up and bends away.

Reflection of a wave: angle of incidence equals angle of reflection.

Refraction of a wave: light bends toward the normal when entering water.

Slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

Practice questions

Free preview — 8 of 40 questions. Sign up to see them all.

1.Which of the following is a definition of a wave?
Easy
- AA propagating dynamic disturbance of one or more quantities
- BA static change in a physical property
- CA particle moving through a medium
- DA periodic oscillation without energy transfer
2.What is the term for the maximum displacement of a wave from its equilibrium position?
Easy
- AAmplitude
- BWavelength
- CFrequency
- DPeriod
3.Which of the following types of waves requires a physical medium to travel?
Easy
- AElectromagnetic wave
- BMechanical wave
- CGravitational wave
- DAll waves
4.In a transverse wave, the direction of particle vibration is:
Medium
- AParallel to the direction of wave propagation
- BPerpendicular to the direction of wave propagation
- CCircular around the direction of propagation
- DRandom with respect to propagation
5.What does the frequency of a wave measure?
Medium
- AThe number of waves passing a point per unit time
- BThe distance between two consecutive crests
- CThe maximum displacement from equilibrium
- DThe time for one complete wave to pass
6.A wave has a frequency of 5 Hz. How many waves pass a point in 2 seconds?
Medium
- A2.5
- B5
- C10
- D20
7.Which of the following is true about sound waves in air?
Hard
- AThey are transverse waves
- BThey are longitudinal waves
- CThey can travel through a vacuum
- DThey are electromagnetic waves
8.What is the relationship between wave speed (v), frequency (f), and wavelength (λ)?
Hard
- Av = f × λ
- Bv = f / λ
- Cv = λ / f
- Dv = f + λ

Revision notes

## Wave Properties - Quick Revision ### What is a wave? A wave is a **disturbance** that travels through a medium or space, transferring energy and momentum without permanently moving matter. Waves can be **periodic** (repeating pattern) or **pulse** (single disturbance). ### Key Properties - **Amplitude (A)**: Maximum displacement from equilibrium (rest position). Larger amplitude = more energy. - **Wavelength (λ)**: Distance between two consecutive identical points (e.g., crest to crest). - **Frequency (f)**: Number of complete waves passing a point per second. Unit: hertz (Hz). - **Wave speed (v)**: Speed at which the wave travels. Formula: **v = f × λ** ### Types of Waves - **Transverse waves**: Particles vibrate perpendicular to wave direction. Example: light, waves on a string. - **Longitudinal waves**: Particles vibrate parallel to wave direction. Example: sound waves (compressions and rarefactions). ### Mechanical vs. Electromagnetic Waves - **Mechanical waves**: Need a medium (solid, liquid, gas). Examples: sound, seismic waves, water waves. - **Electromagnetic waves**: Can travel through vacuum. Examples: light, radio waves, X-rays. All travel at speed of light (3×10⁸ m/s in vacuum). ### Energy and Waves Waves carry **energy**. The energy transported depends on amplitude (higher amplitude = more energy). For mechanical waves, energy also depends on frequency. ### Key Formulas - Wave speed: **v = f × λ** - Frequency: **f = 1 / T** (T = period, time for one complete wave) ### Important Points - In a **standing wave**, two identical waves traveling opposite directions create nodes (points of no displacement) and antinodes (maximum displacement). - Sound waves in air are **longitudinal**; light waves are **transverse**. - Waves can be reflected, refracted, diffracted, and interfere.

Amplitude: The maximum displacement of a point on a wave from its equilibrium position; related to the energy carried by the wave.
Wavelength: The distance between successive identical points on a wave (e.g., crest to crest or trough to trough).
Frequency: The number of complete waves that pass a point per unit time; measured in hertz (Hz).
Wave speed: The speed at which a wave travels through a medium; calculated as v = f × λ.
Transverse wave: A wave in which the disturbance is perpendicular to the direction of propagation (e.g., light, waves on a string).
Longitudinal wave: A wave in which the disturbance is parallel to the direction of propagation (e.g., sound waves in air).
Mechanical wave: A wave that requires a medium to travel through (e.g., sound, water waves).
Electromagnetic wave: A wave that can travel through a vacuum, consisting of oscillating electric and magnetic fields (e.g., light, radio waves).
Standing wave: A wave pattern that results from the interference of two identical waves traveling in opposite directions; has nodes and antinodes.
Period: The time taken for one complete wave to pass a point; T = 1/f.

Flashcards

What is a wave?

A wave is a propagating disturbance that carries energy and momentum from one place to another without permanently transferring matter.

What is amplitude?

Amplitude is the maximum displacement of a wave from its equilibrium position. It relates to the energy carried by the wave: higher amplitude means more energy.

What is wavelength?

Wavelength is the distance between two consecutive corresponding points on a wave, such as crest to crest or trough to trough. It is usually measured in meters.

What is frequency?

Frequency is the number of complete wave cycles that pass a point per unit time, typically measured in hertz (Hz). It is inversely related to wavelength.

How are wavelength and frequency related?

Wavelength and frequency are inversely related: as wavelength increases, frequency decreases, and vice versa, assuming constant wave speed.

What is the wave speed equation?

Wave speed (v) equals frequency (f) times wavelength (λ): v = f × λ.

What is a transverse wave?

In a transverse wave, the disturbance moves perpendicular to the direction of wave travel. Example: waves on a string.

What is a longitudinal wave?

In a longitudinal wave, the disturbance moves parallel to the direction of wave travel. Example: sound waves in air.

Give an example of a transverse wave.

Light waves (electromagnetic waves) are transverse. Also, waves on a string or water waves (surface waves have both transverse and longitudinal components).

Give an example of a longitudinal wave.

Sound waves in air are longitudinal. They consist of compressions and rarefactions moving through the medium.

What is a mechanical wave?

A mechanical wave requires a medium (solid, liquid, or gas) to travel through. Examples: sound waves, seismic waves, water waves.

What is an electromagnetic wave?

An electromagnetic wave does not require a medium; it can travel through vacuum. Examples: light, radio waves, X-rays.

How does energy relate to amplitude?

The energy carried by a wave is proportional to the square of its amplitude. Doubling the amplitude quadruples the energy.

What is a crest?

A crest is the highest point of a wave above the equilibrium position.

What is a trough?

A trough is the lowest point of a wave below the equilibrium position.

What is a compression?

In a longitudinal wave, a compression is a region where particles are close together (high pressure).

What is a rarefaction?

In a longitudinal wave, a rarefaction is a region where particles are spread apart (low pressure).

What is a standing wave?

A standing wave is formed by two identical waves traveling in opposite directions. It has nodes (points of no displacement) and antinodes (points of maximum displacement).

What is a node?

A node is a point on a standing wave where the amplitude is always zero (no vibration).

What is an antinode?

An antinode is a point on a standing wave where the amplitude is maximum.

What is the period of a wave?

The period is the time it takes for one complete wave cycle to pass a point. It is the reciprocal of frequency: T = 1/f.

How do you calculate wave speed?

Wave speed (v) = frequency (f) × wavelength (λ). Also, v = distance / time for a wave pulse.

What happens to wave speed when the medium changes?

Wave speed depends on the medium. For example, sound travels faster in solids than in gases, and light travels slower in water than in vacuum.

What is polarization?

Polarization describes the direction of oscillation in a transverse wave. For example, light can be polarized to oscillate in a single plane.

Unlock all 40 questions, flashcards & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

Coming soon