Waves

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Separate wave travel from movement of water in a model
Describe reflection and superposition using evidence

Vocabulary: oscillation · transverse model · amplitude · reflection · superposition · wavefront

Retrieve previous learning

How does a reflected ray help describe light at a mirror?

Check: A ray shows the direction light travels, and a reflected ray changes direction at the surface under the reflection rule.

Learn the concept

A water-surface disturbance can travel across water while a small floating marker mainly oscillates near its starting position. The marker does not usually travel with the crest across the whole tank. This distinction separates movement of a wave pattern, which transfers energy, from bulk transport of the water. In a simplified classroom model the surface moves up and down while the wave travels horizontally, giving a transverse picture in which the motions are at right angles.

Real surface-water particles can move in more complicated paths, often with horizontal as well as vertical components. Therefore the up-down transverse drawing is a useful model rather than a complete account of every particle path. Amplitude is the maximum displacement from the undisturbed level, not the height from trough to crest. A wavefront line can mark corresponding crests and help show the direction the pattern moves.

A wave reaching a barrier may reflect and travel in a new direction. With an ideal straight barrier and suitable conditions, reflection can be represented by equal angles to the normal. The reflected pattern is not a new substance and the barrier need not move with the wave. A supplied diagram should distinguish incident direction, boundary and reflected direction rather than drawing the wave straight through an opaque barrier.

When two disturbances overlap, their displacements combine at that place and time: two upward disturbances can make a larger displacement, while opposite displacements can partly or briefly cancel. After crossing, the waves can continue; temporary cancellation is not destruction of energy. A teacher may demonstrate with approved equipment, but this written lesson does not instruct learners to create waves in open water. Water demonstrations need a school risk assessment and supervision.

Worked model

Read a diagram with a marked floating point and trace a crest moving right.
Mark the point oscillating near its initial position rather than riding with the crest.
Use an ideal straight barrier to draw a reflected wave direction and identify the normal.
Add two supplied displacements at one place, then explain temporary reinforcement or cancellation.

Guided practice

Two model pulses overlap with displacements +2 cm and -1 cm. What is the instant displacement?

Hint: Add signed displacements.

Check the guided answer

The instant resultant displacement is +1 cm. This is temporary superposition; it does not mean one whole wave has permanently vanished.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“The same water travels across the tank with each crest.”

Correction: The wave pattern can travel while water near a point oscillates; the simple transverse drawing has limits for real surface waves.

Extend and reflect

Why might a wavefront diagram be better than one floating-marker path for reflection?

Guidance: Compare how each represents the travelling pattern versus motion of one part of the medium.

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Physical Sciences

This lesson practises: Separate wave travel from movement of water in a model. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Physical Sciences. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Laboratory Data Analyst. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.

Year 9 · Physics: waves · original lesson pack

DASKEREL beta · internal AI review pending

Sound waves in material media

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Describe longitudinal particle vibration and energy transfer
Compare sound travel in gas, liquid and solid with stated limits

Vocabulary: vibration · longitudinal · compression · rarefaction · medium · vacuum

Retrieve previous learning

What is the difference between a travelling water-wave crest and one marked point of water?

Check: The crest pattern travels across the surface while the marked region mainly oscillates near its starting location.

Learn the concept

A vibrating source can disturb nearby material and produce a sound wave. In air, molecules oscillate back and forth around their positions as regions of higher pressure and lower pressure travel away. The oscillation direction is parallel to the wave's direction of travel, so sound in air is modelled as a longitudinal pressure wave. The same air molecule does not need to travel from a speaker to a listener for sound energy and information to reach the listener.

A compression is a region where particles are temporarily closer together than average; a rarefaction is a region where they are farther apart. A sketch with crowded dots can represent these regions, but it is not a scale photograph or a claim that air is permanently bunched up. Sound needs a material medium. In a vacuum there are no material particles to pass on this mechanical disturbance, whereas light can travel through a vacuum.

Sound can travel through gases, liquids and solids. For common classroom examples it travels faster through water than air and faster through many solids than through water, but speed depends on the particular material and conditions, including temperature. Do not infer a universal ranking for every possible solid and liquid solely from their state names. Stronger coupling and material stiffness help transfer a disturbance, while density also matters.

A sound source, such as a loudspeaker diaphragm, vibrates and causes neighbouring medium particles to vibrate; a microphone diaphragm can detect the arriving disturbance. Reflection at a hard surface may produce an echo, while some materials absorb more sound energy. This page relies on diagrams and supplied evidence. No one should produce very loud sounds or press ears against devices to test the model; a teacher controls any demonstration and hearing safety.

Worked model

Mark a vibrating source and nearby air particles oscillating parallel to travel direction.
Label a crowded region compression and a spread-out region rarefaction in a supplied diagram.
Trace energy transfer through the medium without drawing one particle travelling the whole distance.
Compare supplied air, water and solid speed values while naming the material and temperature limits.

Guided practice

Can a bell's sound cross an ideal vacuum?

Hint: What carries a mechanical sound wave?

Check the guided answer

No. Sound needs material particles to pass on a pressure disturbance. Light could cross the vacuum, but the mechanical sound wave cannot.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“A parcel of air must travel from the speaker to the ear to carry sound.”

Correction: Air particles vibrate locally while the pressure disturbance moves through the medium.

Extend and reflect

Why can a hard wall give an echo while a soft surface may weaken it?

Guidance: Compare reflected and absorbed sound energy using stated material evidence rather than assuming perfectly reflecting or absorbing surfaces.

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Physical Sciences

This lesson practises: Describe longitudinal particle vibration and energy transfer. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Physical Sciences. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Laboratory Data Analyst. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.

Year 9 · Physics: waves · original lesson pack

DASKEREL beta · internal AI review pending

Speed of sound from echo data

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Calculate sound speed from a reflected out-and-back path
Evaluate timing and distance uncertainty

Vocabulary: speed · echo · reflection · distance · time · metres per second

Retrieve previous learning

Why does sound not cross a vacuum?

Check: A mechanical sound wave needs a material medium whose particles pass on the travelling disturbance.

Learn the concept

Speed describes distance travelled per unit time: speed = distance ÷ time, usually in metres per second (m/s). Sound speed in air near ordinary room conditions is roughly 340 m/s, but it changes with temperature and other conditions. An echo occurs when a sound pulse reflects from a surface and returns. The echo delay includes travel to the surface and back, so the sound's path is twice the one-way distance when the source and listener are effectively together.

For a supplied example, a reflector is 170 m away and the pulse returns after 1.0 s. The travel distance is 2 × 170 = 340 m, giving speed 340 m ÷ 1.0 s = 340 m/s. Dividing 170 by 1.0 would give the wrong speed because it forgets the return journey. If source and receiver are far apart, the path geometry needs separate treatment; the simple doubled distance applies only to the stated arrangement.

Timing uncertainty matters. A human may react late when starting or stopping a stopwatch, and a faint echo may be hard to distinguish from background noise. A longer path or repeated pulses under teacher control can reduce the proportion of a fixed timing error, but may introduce other limits such as weaker echoes or uncertain reflector distance. Record units, conditions, method and spread of repeated values rather than presenting 340.000 m/s as exact.

Use a provided dataset for independent calculations. This lesson does not ask learners to create loud impulses, visit roadside or isolated echo sites, or test hearing limits. Any practical echo demonstration needs a teacher's risk assessment, location permission and control of noise exposure. A calculated result from written data does not establish practical measurement competence. Sound travels at different speeds in different media, so an air value cannot be applied automatically to water or steel.

Worked model

Read a supplied one-way reflector distance of 102 m and an echo delay of 0.60 s.
Double the path because sound travels out and back: 2 × 102 m = 204 m.
Divide distance by time: 204 m ÷ 0.60 s = 340 m/s.
State that the estimate is for air under the supplied conditions and identify one timing uncertainty.

Guided practice

An echo returns after 0.50 s from a wall 85 m away. What is the estimated speed?

Hint: Use the round-trip path.

Check the guided answer

The path is 2 × 85 = 170 m. Dividing by 0.50 s gives an estimated speed of 340 m/s for those conditions.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“Echo time measures only the outward sound journey.”

Correction: The delay includes the out-and-back path when source and receiver are together, so use twice the wall distance.

Extend and reflect

Why could two echo estimates differ on a warmer and cooler day?

Guidance: State that sound speed in air changes with temperature, while measurement uncertainty must also be considered.

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Physical Sciences

This lesson practises: Calculate sound speed from a reflected out-and-back path. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Physical Sciences. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Laboratory Data Analyst. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.

Year 9 · Physics: waves · original lesson pack

DASKEREL beta · internal AI review pending

Hearing: from wave to nerve signal

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Trace the hearing pathway from pressure wave to brain
Interpret typical hearing-frequency range without treating it as a diagnosis

Vocabulary: frequency · hertz · eardrum · cochlea · hair cell · auditory nerve

Retrieve previous learning

Why is a wall distance doubled in a simple echo calculation?

Check: A pulse travels from the source to the reflector and returns to the nearby receiver, so the delay covers both legs.

Learn the concept

A travelling sound-pressure wave reaches the ear and makes the eardrum vibrate. Small bones in the middle ear pass the vibration to the fluid-filled cochlea. Specialised sensory hair cells respond and help produce electrical nerve signals that travel towards the brain. The brain interprets these signals as a hearing experience. This chain links physical wave motion to biology; it is not a claim that air molecules travel through the ear all the way to the brain.

Frequency is the number of oscillations per second and is measured in hertz (Hz). Frequency is strongly related to perceived pitch for a simple tone. Amplitude describes the size of the pressure variation and contributes to perceived loudness, but perceived loudness also depends on frequency, duration and the listener. Avoid treating pitch and loudness as the same quantity. A microphone can convert a sound-induced motion into an electrical signal, but a microphone is not itself conscious of a sound.

A conventional approximate hearing range for many young healthy humans is 20 Hz to 20,000 Hz (20 kHz). Individual limits vary with age, hearing history and conditions. Below about 20 Hz is called infrasound; above about 20 kHz is ultrasound. Outside a person's audible range does not imply the wave is absent or safe at high intensity. Other animals may detect frequencies outside a typical human range. A frequency chart is not a hearing test or a basis for diagnosing a person.

Hearing protection matters because sufficiently intense sound or long exposure can harm hearing. Learners should not raise headphone volume or generate extreme tones to check a limit, and no one should infer a health condition from an online activity. Supplied diagrams and frequency data support this written lesson. Any demonstration must be teacher-controlled, use safe levels and offer accessible alternatives. Concerns about hearing belong with a trusted adult or qualified health professional.

Worked model

Trace a supplied arrow from incoming sound wave to vibrating eardrum.
Continue through middle-ear bones and the cochlea's sensory cells to nerve signals and brain interpretation.
Classify a supplied 1,000 Hz tone within the typical human range and a 25,000 Hz sound wave as ultrasound.
Separate frequency-related pitch from amplitude-related loudness and state that individual hearing varies.

Guided practice

Is a 25 kHz sound necessarily harmless because it is above a typical human hearing range?

Hint: Separate audibility from energy exposure.

Check the guided answer

No. It is ultrasound by frequency, but inaudibility does not establish safety. Exposure depends on intensity and duration and requires appropriate controls.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“A sound outside my hearing range is absent or harmless.”

Correction: A pressure wave may still exist, and safety depends on exposure, not merely whether one listener hears it.

Extend and reflect

Why might two people report different high-frequency hearing limits?

Guidance: Mention individual and age-related variation; avoid making a diagnosis from an uncalibrated sound source.

Where this lesson could lead · Combined Science: Trilogy GCSE → Daskerel Physical Sciences

This lesson practises: Trace the hearing pathway from pressure wave to brain. Scientific explanation, measurement and evidence support later laboratory, technical and quality work.

Next school subject: Combined Science: Trilogy GCSE. Check the subject and examination board that fit your school.
Later DASKEREL learning: Daskerel Physical Sciences. Explore further study and build evidence from practical work.
Later credential exploration: No subject-specific professional credential is mapped from this lesson. Explore the credential catalogue after choosing a later specialism.
Example career direction: Laboratory Data Analyst. Explore organisations and local support.

This is an exploratory route, not a promise of admission, a qualification, certification eligibility or employment. Years 7–9 learning is an early foundation; any later credential may require substantial study, experience or local approval.

Year 9 · Physics: waves · original lesson pack

DASKEREL beta · internal AI review pending

Ultrasound: echoes, imaging and controlled uses

DASKEREL wrote this teaching and practice using Oak's sequence as a source. View the source lesson at Oak National Academy. Oak has not endorsed this material. Check Oak's terms and separate rights for third-party works.

Learning outcomes

Classify ultrasound by frequency and explain how pulse echoes can locate a boundary
Distinguish clinical and industrial uses from claims of automatic safety

Vocabulary: ultrasound · frequency · pulse · echo · boundary · non-ionising

Retrieve previous learning

Why is an inaudible sound not automatically harmless?

Check: Audibility depends on a listener's hearing range, whereas the effect of a sound exposure depends on factors such as intensity, duration and its interaction with material.

Learn the concept

Ultrasound is sound with frequency above the conventional upper limit of human hearing, about 20,000 Hz or 20 kHz. It remains a mechanical wave: it needs a material medium and can reflect at a boundary where properties change. A 25 kHz sound wave is classified as ultrasound; the frequency alone does not state its amplitude, energy exposure or safety. Some animals can detect higher frequencies than many humans, so the classification refers to a typical human range, not to every living ear.

A transmitter can send a short ultrasound pulse into a medium and a receiver can detect part of it after reflection. If the speed in that medium and the out-and-back time are known, a simple boundary depth is speed multiplied by time and divided by two. The division by two matters because the pulse travels to the boundary and returns. The simple calculation assumes an identifiable path and an appropriate speed; a real image may require many pulses, computer processing and allowance for different materials.

Diagnostic ultrasound can form images from returning echoes at tissue boundaries. It uses non-ionising sound rather than the ionising radiation used in X-ray imaging. That distinction does not make every ultrasound exposure or device setting automatically risk-free. Clinical staff select the equipment and exposure, interpret images and consider limitations such as poor transmission through air-filled regions or obstruction by bone. A classroom calculation is not an image interpretation or medical diagnosis.

Ultrasound can also be used in controlled cleaning systems and, under qualified professional supervision, in some physiotherapy services; these uses have different purposes, intensities and effects. This written lesson offers no treatment guidance. No learner should operate a clinical or industrial ultrasound device to test this lesson. Use supplied pulse data and diagrams only. A trained professional and the relevant risk assessment govern any demonstration or practical use, while questions about personal health should be addressed to an appropriate healthcare professional.

Worked model

Classify a supplied 25,000 Hz sound wave as ultrasound because it exceeds 20,000 Hz.
Read a supplied pulse-echo delay of 0.00008 s and a stated speed of 1,500 m/s in a model tissue.
Calculate the round-trip distance as 1,500 × 0.00008 = 0.12 m, then halve it to 0.06 m or 6 cm.
Explain that a boundary estimate depends on the assumed speed and path, so a trained clinician interprets any actual image.

Guided practice

A 30 kHz sound pulse returns after 0.00004 s in a medium with stated speed 1,500 m/s. Estimate boundary depth.

Hint: The pulse covers the path twice.

Check the guided answer

The full path is 1,500 × 0.00004 = 0.06 m; the one-way depth is 0.03 m, or 3 cm, under the stated speed and path assumptions.

Independent practice

Write your own response to every question before viewing the model answers. Your writing stays in this page session; this activity does not submit, store or grade it. Avoid including private information.

Find and correct a misconception

“Ultrasound is inaudible, so every device using it is harmless.”

Correction: Being above a conventional hearing limit does not determine exposure or risk; safe clinical and industrial use depends on trained practice and appropriate controls.

Extend and reflect

Why might a simple one-speed calculation give a poor estimate when a pulse crosses several materials?

Guidance: Different media can have different sound speeds and reflections, so a single speed and single path may not describe all returning echoes.