Why is sound in air described as a longitudinal wave?

The air moves backwards and forwards along the direction the wave travels, forming compressions and rarefactions.

Describe a way of measuring the speed of ripples by timing them.

Time how long a single ripple takes to cross a measured distance in the tank, then divide the distance by the time.

Describe a way of finding the speed of ripples using the wave equation.

Count the number of ripples produced each second and measure the distance between crests, then multiply the frequency by the wavelength.

Describe how the speed of sound in air can be measured outdoors over a long distance.

Stand a measured distance from someone making a sharp sound, time the gap between seeing the sound being made and hearing it, then divide the distance by the time.

Describe how two microphones and a timer can be used to measure the speed of sound in a laboratory.

Place the microphones a measured distance apart in line with the source and record the time between the sound reaching each one, then divide the separation by that time.

OCR GCSE Combined Science Physics J250

Electricity

Topic overview Charge, and producing static electricity Transfer of electrons in charging and discharging Current as a rate of flow of charge Charge, current and time Series and parallel circuits, and circuit symbols Current, potential difference and resistance Resistors whose resistance changes, and investigating them Linear and non-linear circuit elements from graphs Net resistance in series and parallel Circuits for measurement, and electrical power

Energy

Topic overview Conservation of energy, and energy stores Energy changes on heating, and calculating them Energy of a moving body, a spring and a raised object Dissipation, and energy transfer in domestic devices Power ratings, and calculating efficiency Reducing unwanted energy transfer, and the rate of cooling

Forces

Topic overview Measuring distance and time, and calculating speed Converting units, and rates Vectors and scalars in motion Distance-time and velocity-time graphs Average speed, and the equations of uniform motion How objects interact, and forces as vectors Newton's first law Newton's second law Work done, and stored energy Power, and Newton's third law Stretching, bending and compressing; elastic and plastic Force and extension, linear and non-linear The spring constant, and work done in stretching Gravitational fields, weight and free fall Calculations with weight and gravitational field strength

Global Challenges

Topic overview Typical speeds and everyday accelerations Reaction time, stopping distance and the dangers of large decelerations Stopping distance, acceleration and collision force calculations Energy resources, and trends in their use The national grid, and step-up and step-down transformers Why the national grid is efficient, and power in a transformer Mains electricity: a.c., d.c. and the domestic supply Live, neutral and earth wires, and electrical danger

Magnetism and Magnetic Fields

Topic overview Permanent and induced magnets, and magnetic poles Magnetic fields, and the dipping compass The magnetic effect of a current, and solenoids

Matter

Topic overview How the atomic model changed, and the structure of the atom The size of atoms, and defining density Density of the states of matter, and density calculations Conservation of mass in changes of state Heating a system, and specific heat capacity Calculations with specific heat capacity and latent heat Gas molecules, temperature and pressure

Radioactivity

Topic overview Protons, neutrons and isotopes Unstable nuclei and the emissions they give out Balancing nuclear equations Electron energy levels, and radiation from atoms Half-life and the randomness of decay Penetration of alpha, beta and gamma Contamination and irradiation, and reducing the hazard

Waves in Matter

Topic overview Amplitude, wavelength, frequency and period The wave equation Transverse and longitudinal waves Modelling waves with ripples and sound Electromagnetic waves as transverse, and energy transfer Frequency and wavelength across the spectrum What our eyes detect, and light as an electromagnetic wave Uses of electromagnetic waves Hazards of ultraviolet, X-rays and gamma rays Investigating reflection and refraction of light

Waves in Matter

Modelling waves with ripples and sound

3 things to know
Paper 6 (Physics)

Overview

Why ripples model transverse waves and sound longitudinal ones, methods for measuring the speed of ripples and of sound, and the evidence that waves transfer energy without moving matter along.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why do ripples model a transverse wave and sound, forming compressions and rarefactions, a longitudinal one, and how can the speed of ripples be timed?

Key term

Roughly how does the speed of sound in air compare with the speed of ripples on water?

Key term

Explain why ripples on water are used as a model of a transverse wave.

Questions from this subtopic

Each one with the model answer underneath.

1
Explain why ripples on water are used as a model of a transverse wave.
Model answer
The water surface moves up and down while the ripple travels sideways, so the vibration is at right angles to the direction of travel.
2
Why is sound in air described as a longitudinal wave?
Model answer
The air moves backwards and forwards along the direction the wave travels, forming compressions and rarefactions.
3
Describe a way of measuring the speed of ripples by timing them.
Model answer
Time how long a single ripple takes to cross a measured distance in the tank, then divide the distance by the time.
4
Describe a way of finding the speed of ripples using the wave equation.
Model answer
Count the number of ripples produced each second and measure the distance between crests, then multiply the frequency by the wavelength.
5
Describe how the speed of sound in air can be measured outdoors over a long distance.
Model answer
Stand a measured distance from someone making a sharp sound, time the gap between seeing the sound being made and hearing it, then divide the distance by the time.
6
Describe how two microphones and a timer can be used to measure the speed of sound in a laboratory.
Model answer
Place the microphones a measured distance apart in line with the source and record the time between the sound reaching each one, then divide the separation by that time.

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Electricity

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Forces

Global Challenges

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