Waves

Know that waves transfer energy without transferring matter

Describe what is meant by wave motion as illustrated by vibrations in ropes and springs, and by experiments using water waves

Describe the features of a wave in terms of wavefront, wavelength, frequency, crest (peak), trough, amplitude and wave speed

Recall and use the equation for wave speed v = fλ

Know that 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

Know that 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

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

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

Describe how wavelength and gap size affects diffraction through a gap

Describe how wavelength affects diffraction at an edge

Define and use the terms normal, angle of incidence and angle of reflection

Describe the formation of an optical image by a plane mirror and give its characteristics, i.e. same size, same distance from mirror, virtual

State that for reflection, the angle of incidence is equal to the angle of reflection; recall and use this relationship

Use simple constructions, measurements and calculations for reflection by plane mirrors

Define and use the terms normal, angle of incidence and angle of refraction

Describe an experiment to show refraction of light by transparent blocks of different shapes

Describe the passage of light through a transparent material (limited to the boundaries between two mediums only)

State the meaning of critical angle

Describe internal reflection and total internal reflection using both experimental and everyday examples

Define refractive index, n, as the ratio of the speeds of a wave in two different regions

Recall and use the equation sin i n = sin r

Recall and use the equation 1 n = sin c

Describe the use of optical fibres, particularly in telecommunications

Describe the action of thin converging and thin diverging lenses on a parallel beam of light

Define and use the terms focal length, principal axis and principal focus (focal point)

Draw and use ray diagrams for the formation of a real image by a converging lens

Describe the characteristics of an image using the terms enlarged/same size/diminished, upright/inverted and real/virtual

Know that a virtual image is formed when diverging rays are extrapolated backwards and does not form a visible projection on a screen

Draw and use ray diagrams for the formation of a virtual image by a converging lens

Describe the use of a single lens as a magnifying glass

Describe the use of converging and diverging lenses to correct long-sightedness and short- sightedness

Describe the dispersion of light as illustrated by the refraction of white light by a glass prism

Know the traditional seven colours of the visible spectrum in order of frequency and in order of wavelength

Recall that visible light of a single frequency is described as monochromatic

Know the main regions of the electromagnetic spectrum in order of frequency and in order of wavelength

Know that all electromagnetic waves travel at the same high speed in a vacuum

Describe typical uses of the different regions of the electromagnetic spectrum including: (a) radio waves; radio and television transmissions, astronomy, radio frequency identification (RFID) (b) microwaves; satellite television, mobile phones (cell phones), microwave ovens (c) infrared; electric grills, short range communications such as remote controllers for televisions, intruder alarms, thermal imaging, optical fibres (d) visible light; vision, photography, illumination (e) ultraviolet; security marking, detecting fake bank notes, sterilising water (f) X-rays; medical scanning, security scanners (g) gamma rays; sterilising food and medical equipment, detection of cancer and its treatment

Describe the harmful effects on people of excessive exposure to electromagnetic radiation, including: (a) microwaves; internal heating of body cells (b) infrared; skin burns (c) ultraviolet; damage to surface cells and eyes, leading to skin cancer and eye conditions (d) X-rays and gamma rays; mutation or damage to cells in the body

Know that 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

Know that the speed of electromagnetic waves in a vacuum is 3.0 × 108 m / s and is approximately the same in air

Know that many important systems of communications rely on electromagnetic radiation including: (a) mobile phones (cell phones) and wireless internet use microwaves because microwaves can penetrate some walls and only require a short aerial for transmission and reception (b) Bluetooth uses radio waves because radio waves pass through walls but the signal is weakened on doing so (c) optical fibres (visible light or infrared) are used for cable television and high-speed broadband because glass is transparent to visible light and some infrared; visible light and short wavelength infrared can carry high rates of data

Know the difference between a digital and analogue signal

Know that a sound can be transmitted as a digital or analogue signal

Explain the benefits of digital signalling including increased rate of transmission of data and increased range due to accurate signal regeneration

Describe the production of sound by vibrating sources

Describe the longitudinal nature of sound waves

State the approximate range of frequencies audible to humans as 20 Hz to 20 000 Hz

Know that a medium is needed to transmit sound waves

Know that the speed of sound in air is approximately 330–350 m / s

Describe a method involving a measurement of distance and time for determining the speed of sound in air

Describe how changes in amplitude and frequency affect the loudness and pitch of sound waves

Describe an echo as the reflection of sound waves

Define ultrasound as sound with a frequency higher than 20 kHz

Describe compression and rarefaction

Know that, in general, sound travels faster in solids than in liquids and faster in liquids than in gases

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