# Year 9 Wave Properties Objectives • Waves may be either transverse or longitudinal.
• The ripples on a water surface are an example of a transverse wave.
• Longitudinal waves show areas of compression and rarefaction.
• Sound waves travelling through air are longitudinal.
• Students should be able to describe the difference between longitudinal and transverse waves.
• Students should be able to describe evidence that, for both ripples on a water surface and sound waves in air, it is the wave and not the water or air itself that travels.
• Students should be able to describe wave motion in terms of their amplitude, wavelength, frequency and period.
• The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position.
• The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave.
• The frequency of a wave is the number of waves passing a point each second.
• period = 1 /frequency (T = 1/f)
• The wave speed is the speed at which the energy is transferred (or the wave moves) through the medium.
• All waves obey the wave equation: wave speed = frequency× wavelength (v = f λ)
• Students should be able to:
• identify amplitude and wavelength from given diagrams
• recall and apply this equation.
• describe a method to measure the speed of sound waves in air
• describe a method to measure the speed of ripples on a water surface.
• Students should be able to show how changes in velocity, frequency and wavelength, in transmission of sound waves from one medium to another, are inter-related.
• Waves can be reflected at the boundary between two different materials.
• Waves can be absorbed or transmitted at the boundary between two different materials.
• Students should be able to construct ray diagrams to illustrate the reflection of a wave at a surface.
• Students should be able to describe the effects of reflection, transmission and absorption of waves at material interfaces.
• Different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with wavelength.
• Some effects, for example refraction, are due to the difference in velocity of the waves in different substances.
• Students should be able to construct ray diagrams to illustrate the refraction of a wave at the boundary between two different media.
• Students should be able to use wave front diagrams to explain refraction in terms of the change of speed that happens when a wave travels from one medium to a different medium.
• Each colour within the visible light spectrum has its own narrow band of wavelength and frequency.
• Reflection from a smooth surface in a single direction is called specular reflection.
• Reflection from a rough surface causes scattering: this is called diffuse reflection.
• Colour filters work by absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour).
• The colour of an opaque object is determined by which wavelengths of light are more strongly reflected. Wavelengths that are not reflected are absorbed.
• If all wavelengths are reflected equally the object appears white.
• If all wavelengths are absorbed the objects appears black.
• Objects that transmit light are either transparent or translucent.
• Students should be able to explain:
• how the colour of an object is related to the differential absorption, transmission and reflection of different wavelengths of light by the object
• the effect of viewing objects through filters or the effect on light of passing through filters
• why an opaque object has a particular colour.
• LOGON SCIENCE CODES - 4.6.1.1, 4.6.1.2, 4.6.1.4, 4.6.2.2 (ignore references to electromagnetic spectrum for this module)  