wave - A way of transferring energy or information. Many waves travel when particles pass on vibrations., longitudinal wave - A wave where the particles vibrate parallel to the direction the wave is travelling., transverse wave - A wave where the vibrations are perpendicular to the direction the wave is travelling., amplitude - The size of vibrations or the maximum distance a particle moves away from its resting position when a wave passes., wavelength - The distance between a point on one wave and the same point on the next wave., period - The time taken for one complete wave to pass a point. It is measured in seconds., frequency - The number of vibrations (or the number of waves) per second., hertz (Hz) - The unit for frequency. One hertz is one wave per second., velocity - The speed of an object in a particular direction. Usually measured in metres per second (m/s)., seismic waves - Vibrations in the rocks of the Earth caused by earthquakes or explosions. There are transverse and longitudinal seismic waves., sound waves - Vibrations in the particles of a solid, liquid or gas, which are detected by our ears and ‘heard’ as sounds. Sound waves are longitudinal waves., electromagnetic waves - A group of waves that all travel at the same speed in a vacuum and are all transverse., absorb - When a wave disappears as the energy it is carrying transfers to the medium through which it is travelling., transmit - When a wave passes through a material and is not absorbed or reflected., refraction - The change in direction when waves go from one medium to another., medium - Any substance through which something travels., interface - The boundary between two materials., auditory nerve - The nerve that carries impulses from an ear to the brain., cochlea - The part of the ear that changes vibrations into electrical impulses., ear canal - The tube in the head that leads to the eardrum., eardrum - A thin membrane inside the ear that vibrates when sound reaches it., impulse - An electrical signal that travels in the nervous system., neurone - A cell that transmits electrical impulses in the nervous system., ultrasound - Sound waves with a frequency above 20 000 Hz, which is too high for the human ear to detect., sonar - A way of finding the distance to an underwater object (such as the sea bed) by timing how long it takes for a pulse of ultrasound to be reflected., ultrasound scan - A way of making an image of part of the body (usually a fetus) using ultrasound waves reflected from parts of the inside of the body., infrasound - Sound waves with a frequency below 20 Hz, which is too low for the human ear to detect., P waves - Longitudinal seismic waves that travel through the Earth., S waves - Transverse seismic waves that travel through the Earth., shadow zone - A part of the Earth’s surface that P or S waves from an earthquake do not reach because they have been reflected or refracted within the Earth.,

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