3. Waves
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3.1 General properties of waves
3.1.1Waves transfer energy without
• Know: waves transfer energy without transferring matter
3.1.2What is meant by wave motion as
• Describe what is meant by wave motion as illustrated by vibrations in ropes and springs, and by experiments using water waves
3.1.3Features of a wave in terms of
• Describe the features of a wave in terms of wavefront, wavelength, frequency, crest (peak), trough, amplitude and wave speed
3.1.4Recall/use: for wave speed v = f λ
• Recall/use: for wave speed v = f λ
3.1.5For a transverse wave, the direction
• Know: for a transverse wave, the direction of vibration is at right angles to the direction of propagation and understand that electromagnetic radiation, water waves and seismic S-waves (secondary) can be modelled as transverse
3.1.6For a longitudinal wave, the direction
• Know: for a longitudinal wave, the direction of vibration is parallel to the direction of propagation and understand that sound waves and seismic P-waves (primary) can be modelled as longitudinal
3.1.7Waves can undergo: (a) reflection at a
• Describe how waves can undergo: (a) reflection at a plane surface (b) refraction due to a change of speed (c) diffraction through a narrow gap
3.1.8Use of a ripple tank to show: (a)
• Describe the use of a ripple tank to show: (a) reflection at a plane surface (b) refraction due to a change in speed caused by a change in depth (c) diffraction due to a gap (d) diffraction due to an edge
3.1.9Wavelength and gap size affects
• Describe how wavelength and gap size affects diffraction through a gap
3.1.10Wavelength affects diffraction at an
• Describe how wavelength affects diffraction at an edge
3.2.1 Reflection of light
3.2.1.1Terms normal, angle of incidence and
• Define and use the terms normal, angle of incidence and angle of reflection
3.2.1.2Formation of an optical image by a
• Describe the formation of an optical image by a plane mirror and give its characteristics, i.e. same size, same distance from mirror, virtual
3.2.1.3For reflection, the angle of incidence
• State: for reflection, the angle of incidence is equal to the angle of reflection; recall and use this relationship
3.2.1.4Simple constructions, measurements and
• Use simple constructions, measurements and calculations for reflection by plane mirrors
3.2.2 Refraction of light
3.2.2.1Terms normal, angle of incidence and
• Define and use the terms normal, angle of incidence and angle of refraction
3.2.2.2An experiment to show refraction of
• Describe an experiment to show refraction of light by transparent blocks of different shapes
3.2.2.3Passage of light through a transparent
• Describe the passage of light through a transparent material (limited to the boundaries between two mediums only)
3.2.2.4Meaning of critical angle
• State the meaning of critical angle
3.2.2.5Internal reflection and total internal
• Describe internal reflection and total internal reflection using both experimental and everyday examples
3.2.2.6Refractive index, n, as the ratio of
• Define refractive index, n, as the ratio of the speeds of a wave in two different regions
3.2.2.7Refractive index: n = sin i / sin r
• Recall/use refractive index: n = sin i / sin r
3.2.2.8Critical angle relation: n = 1 / sin c
• Recall/use critical angle relation: n = 1 / sin c
3.2.2.9Use of optical fibres, particularly in
• Describe the use of optical fibres, particularly in telecommunications
3.2.3 Thin lenses
3.2.3.1Action of thin converging and thin
• Describe the action of thin converging and thin diverging lenses on a parallel beam of light
3.2.3.2Terms focal length, principal axis and
• Define and use the terms focal length, principal axis and principal focus (focal point)
3.2.3.3Ray diagrams for the formation of a
• Draw and use ray diagrams for the formation of a real image by a converging lens
3.2.3.4Characteristics of an image using the
• Describe the characteristics of an image using the terms enlarged/same size/diminished, upright/inverted and real/virtual
3.2.3.5A virtual image is formed when
• Know: a virtual image is formed when diverging rays are extrapolated backwards and does not form a visible projection on a screen
3.2.3.6Ray diagrams for the formation of a
• Draw and use ray diagrams for the formation of a virtual image by a converging lens
3.2.3.7Use of a single lens as a magnifying
• Describe the use of a single lens as a magnifying glass
3.2.3.8Use of converging and diverging lenses
• Describe the use of converging and diverging lenses to correct long-sightedness and short-sightedness
3.2.4 Dispersion of light
3.2.4.1Dispersion of light as illustrated by
• Describe the dispersion of light as illustrated by the refraction of white light by a glass prism
3.2.4.2Traditional seven colours of the
• Know the traditional seven colours of the visible spectrum in order of frequency and in order of wavelength
3.2.4.3Recall that visible light of a single
• Recall that visible light of a single frequency is described as monochromatic
3.3 Electromagnetic spectrum
3.3.1Main regions of the EM spectrum in
• Know the main regions of the electromagnetic spectrum in order of frequency and in order of wavelength
3.3.2All EM waves travel at the same high
• Know: all electromagnetic waves travel at the same high speed in a vacuum
3.3.3EM spectrum uses: (a) radio waves
• Describe typical EM spectrum uses: (a) radio waves: radio/TV, astronomy, RFID (b) microwaves: satellite TV, mobile phones, microwave ovens (c) infrared: grills, remotes, intruder alarms, thermal imaging, optical fibres (d) visible light: vision, photography, illumination (e) ultraviolet: security marking, fake banknote detection, sterilising water (f) X-rays: medical scans, security scanners (g) gamma rays: sterilising food/medical equipment, cancer detection/treatment
3.3.4Harm from excessive EM radiation: (a)
• Describe harm from excessive EM radiation: (a) microwaves: internal body-cell heating (b) infrared: skin burns (c) ultraviolet: surface-cell/eye damage, skin cancer and eye conditions (d) X-rays/gamma rays: mutation or cell damage
3.3.5Communication with artificial
• Know: communication with artificial satellites is mainly by microwaves: (a) some satellite phones use low orbit artificial satellites (b) some satellite phones and direct broadcast satellite television use geostationary satellites
3.3.6Speed of EM waves in a vacuum is 3.0 ×
• Know: the speed of electromagnetic waves in a vacuum is 3.0 × 108 m/s and is approximately the same in air
3.3.7EM radiation: (a) mobile
• Know communication systems using EM radiation: (a) mobile phones/wireless internet use microwaves because they penetrate some walls and need short aerials (b) Bluetooth uses radio waves because they pass through walls but weaken (c) optical fibres use visible/infrared for cable TV and high-speed broadband because glass transmits them and they carry high data rates
3.3.8Difference between a digital and
• Know the difference between a digital and analogue signal
3.3.9A sound can be transmitted as a
• Know: a sound can be transmitted as a digital or analogue signal
3.3.10Benefits of digital signalling
• Explain the benefits of digital signalling including increased rate of transmission of data and increased range due to accurate signal regeneration
3.4 Sound
3.4.1Production of sound by vibrating
• Describe the production of sound by vibrating sources
3.4.2Longitudinal nature of sound waves
• Describe the longitudinal nature of sound waves
3.4.3Approximate range of frequencies
• State the approximate range of frequencies audible to humans as 20 Hz to 20 000 Hz
3.4.4A medium is needed to transmit sound
• Know: a medium is needed to transmit sound waves
3.4.5Speed of sound in air is approximately
• Know: the speed of sound in air is approximately 330–350 m/s
3.4.6Method involving a measurement of
• Describe a method involving a measurement of distance and time for determining the speed of sound in air
3.4.7Changes in amplitude and frequency
• Describe how changes in amplitude and frequency affect the loudness and pitch of sound waves
3.4.8An echo as the reflection of sound
• Describe an echo as the reflection of sound waves
3.4.9Ultrasound as sound with a frequency
• Define ultrasound as sound with a frequency higher than 20 kHz
3.4.10Compression and rarefaction
• Describe compression and rarefaction
3.4.11That, in general, sound travels faster
• Know that, in general, sound travels faster in solids than in liquids and faster in liquids than in gases
3.4.12Uses of ultrasound in non- destructive
• Describe the uses of ultrasound in non- destructive testing of materials, medical scanning of soft tissue and sonar including calculation of depth or distance from time and wave speed