Edexcel GCSE 9-1 Physics : SP4 - Waves

Paper 1 Specification: https://qualifications.pearson.com/content/dam/pdf/GCSE/Science/2016/Specification/GCSE_Physics_Spec.pdf

4.1 Recall that waves transfer energy and information without transferring matter

waves = transfer energy + info, NOT MATTER

4.2 Describe evidence that with water and sound waves it is the wave and not the water or air itself that travels

• particles in the water move up and down as a wave passes

• particles are not carried to the shore.

• sound waves; particles in the material through which the wave is travelling move backwards and forwards as the wave passes

4.3 Define and use the terms frequency and wavelength as applied to waves

frequency: number of waves passing a point each second in hertz (Hz).

• sound λ = pitch

• light λ = colour

4.4 Use the terms amplitude, period, wave velocity and wavefront as applied to waves

amplitude: distance from the middle to peak or trough in m.

• greater the amplitude = louder the sound

period: length of time it takes one wave to pass a given point

wave velocity: speed of the wave in the direction it is traveling, waves travel at different speeds in different materials

wavefront: a surface containing points affected in the same way by a wave at a given time

4.5 Describe longitudinal waves by referring to sound, electromagnetic, seismic and water waves

longitudinal waves:

• the oscillations are in line with, or parallel to, the direction of travel of the wave.

• sound waves are longitudinal as particles in the material through which the wave is travelling move backwards and forwards as the wave passes.

• seismic waves produce longitudinal waves when solid rock material is pushed and pulled

4.5 Describe transverse waves by referring to sound, electromagnetic, seismic and water waves

transverse waves:

• oscillations are perpendicular (90°) to the direction of travel

• waves on the surface of water are transverse.

• particles in the water move up and down as a wave passes

• seismic waves can produce solid rock material which move up or down / side to side

• Electromagnetic waves are transverse and do not need a material to travel through

4.6 Recall and use both the equations below for all waves:

v = f ×λ

OR

s = d/t

4.7 Describe how to measure the velocity of sound in air and ripples on water surfaces

speed of sound in air:

• measure the time it takes for a sound to travel a certain distance

• stand in front of a large wall and measure the time it takes for an echo of a loud sound to reach you

speed of sound as ripples on a water surface:

• measure the time it takes for a wave to travel between two fixed points (buoys)

• speed can be calculated from the time + distance between the points

4.8P Calculate depth or distance from time and wave velocity

rearrange s = d/t equation to get d = s x t

4.9P Describe the effects of:

a) reflection at material interfaces

• wave is sent away from second material back to the first

4.9P Describe the effects of:

b) refraction of waves at material interfaces

• wave hits the boundary at an angle, the wave speed changes, causes a change in direction

4.9P Describe the effects of:

c) transmission of waves at material interfaces

• wave carries on travelling through the new material

4.9P Describe the effects of:

d) absorption of waves at material interfaces

• wave is absorbed by the second material

• wave transfers energy to the material's energy stores

  • as transferring energy to the thermal energy store causes heating

4.10 Explain how waves will be refracted at a boundary in terms of the change of direction and speed

• wave hitting a boundary at an angle changes the speed of the wave; changing the direction of the wave → CHANGING WAVELENGTH!

  • bending toward the normal = wave is slowing down

  • bending away from the normal = wave is speeding up

4.11 Recall that different substances may absorb, transmit, refract or reflect waves in ways that vary with wavelength

different substances may absorb, transmit, refract or reflect waves in ways that vary with wavelength

4.12P Describe the processes which convert wave disturbances between sound waves and vibrations in solids:

a) explain why such processes only work over a limited frequency range

b) use this to explain the way the human ear works

• conversion of sound waves to vibrations of solids works over a limited frequency range → restricts the limits of human hearing

• such processes only work over a limited frequency range so humans can’t hear

4.13P Recall that sound with frequencies greater than 20 000 hertz, Hz, is known as ultrasound

sound with λ ≥ 20,000Hz is classified as ultrasound

4.14P Recall that sound with frequencies less than 20 hertz, Hz, is known as infrasound

sound with λ ≤ 20,000Hz is classified as infrasound

4.15P Explain uses of ultrasound and infrasound, including:

a) sonar

• uses ultrasound to detect objects underwater

• sound wave is reflected off the ocean bottom

• time it takes for the sound wave to return is used to calculate the depth of the water

4.15P Explain uses of ultrasound and infrasound, including:

b) foetal scanning

• ultrasound can be used to construct images of a foetus in the womb

• detector is made up of a transducer that produces and detects a beam of ultrasound waves into the body

• waves are reflected back

• when echoes hit the transducer, they generate electrical signals that are sent to the ultrasound scanner to the transducer by different boundaries between tissues in the path of the beam

• when echoes hit the transducer, they generate electrical signals that are sent to the ultrasound scanner

4.16P Describe how changes, if any, in velocity, frequency and wavelength, in the transmission of sound waves from one medium to another are inter-related

v = f × λ