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waves
| Question | Answer |
|---|---|
| When sounds bounce back (reflect) from hard surfaces this is called an . . . | ECHO |
| When a ray of light is reflected from a shiny surface (e.g. a plane mirror) the angle of incidence is equal to . . . | the angle of reflection. |
| A line drawn at 90 degrees to a surface is called a . . . | NORMAL |
| When rays of light change direction as they cross the boundary between two different substances this is called . . . | REFRACTION |
| Refraction occurs when light travels between two different materials because . . . | the speed of light is different in each material. |
| Sound waves are . . . | LONGITUDINAL waves |
| Light waves are . . . | TRANSVERSE waves |
| Light waves travel at . . . | the speed of LIGHT |
| Sound waves travel much slower than light. Their speed in air is approximately . . . | 330 m/s |
| Sound waves can be reflected and . . . | REFRACTED |
| If waves cross a boundary between two different substances at a right angle, there is . . . | NO change of direction but there is a change of speed. |
| What changes when a light ray crosses a boundary between air and glass, travelling into the glass? | Speed decreases. Wavelength decreases. It refracts towards the normal. |
| If a ray of light travels from glass into air, its speed will . . . | increase. |
| Waves travelling across the surface of water are . . . | transverse waves. |
| Water waves can be . . . | refracted and reflected. |
| When water waves travel from deep water to shallow water they are refracted because . . . | they travel more slowly in shallow water. |
| When a ray of light travels from glass,Perspex or water into air . . . | some light is refracted and some is reflected from the boundary. |
| For light travelling from glass to air, if the angle of incidence is greater than the critical angle what happens? | All of the light is reflected inside the glass. |
| What is the name of the angle of incidence at which light is refracted at right angles to the normal? | Critical angle |
| Light can travel along an optic fibre because of . . . | total internal reflection. |
| Sound waves travel through solids, liquids and gases as . . . | longitudinal waves. |
| When a wave moves through a gap, or past an obstacle, it . . . | spreads out from the edges. This is called diffraction. |
| Diffraction of radio waves can improve radio reception in hilly areas because . .. | the waves bend over the summit and down into the valleys. |
| Diffraction occurs more strongly when . . . | the wavelength is similar to the size of the obstacle. |
| When white light passes through a 60 degree triangular prism . . . | a spectrum of colours is produced. |
| Different colours of light have different . . . | wavelengths. |
| When a spectrum is produced by a prism the effect is called . . . | dispersion. |
| Which colour is refracted most by a prism? | Violet |
| There are many more kinds of radiation than we can see with our eyes. The full range is called the . . . | electromagnetic spectrum |
| The type of electromagnetic radiation which has the longest wavelength is . . . | radio waves. |
| The type of electromagnetic radiation which has the shortest wavelenth is . . . | gamma rays. |
| When radiation is absorbed, the energy it carries makes . . . | the substance which absorbs it hotter. |
| Radio waves are used to . . . | transmit radio and TV programmes between different points on Earth's surface. |
| Longer wavelength radio signals can be reflected from an electrically charged layer in Earth's upper atmosphere called . . . | the ionosphere. |
| Microwave radiation of short wavelength which can pass through Earth's atmosphere is used to . . . | send information to and from satellites and within mobile phone networks. |
| A microwave oven can be used for cooking because . . . | water molecules in food strongly absorb microwaves of the correct wavelength. |
| Toasters, grills and radiant heaters make use of . . . | infra red radiation. |
| A TV remote control uses . . . | infra red radiation. |
| Light can be sent down optical fibres to allow doctors to see inside a patient's body. The device is called an . . . | endoscope. |
| Sunbeds make use of . . . | ultraviolet radiation |
| X-rays are used to produce shadow pictures of bones because . . . | X-rays do not easily pass through bone or metal. |
| Gamma radiation is used to . . . | kill harmful bacteria in food, sterilise surgical instruments and kill cancer cells. |
| Microwaves are absorbed by the water in cells which may be . . . | damaged or killed by the heat released. |
| Infra red is absorbed by the skin and felt as . . . | heat. |
| Ultraviolet can pass through the skin to deeper tissues. The darker the skin . . . | the more UV it absorbs and the less reaches deeper tissues. |
| X-rays and gamma rays mostly pass through soft tissues but some . . . | is absorbed by the cells. |
| High doses of UV, X and gamma radiation can kill normal cells. Lower doses can . . . | cause normal cells to become cancerous. |
| Sounds are produced when object vibrate. The greater the amplitude of vibrations . . . | the louder the sound. |
| The number of complete vibrations (cycles) each second is called the . . . | frequency ( measured in hertz, Hz) |
| Electronic systems can produce waves which have a frequency higher than humans can hear called . . . | ultrasound or ultrasonic waves |
| Ultrasonic waves are used in medicine for . . . | pre-natal scanning |
| The information needed for an ultrasound scan to be useful is . . . | the time taken for an echo to return to the detector. |
| Our knowledge of the structure of the Earth comes from studying how the shock waves from earthquakes travel through it. These are called . . . | seismic waves. |
| Earthquakes produce waves which can be detected using . . . | seismographs or seismometers. |
| What are the two types of seismic waves that travel through the interior of the Earth? | P and S waves. |
| Which type of seismic waves are faster? | Primary (P) waves |
| What is the difference between the two types of seismic waves? | P waves are longitudinal, S waves are transverse. |
| Which type of seismic wave cannot travel in a liquid? | S waves |
| Seismic waves travel in curved paths through the interior of the Earth because . . . | they are being refracted. |
| The speed and direction of P waves change abruptly as they reach the outer core because . . . | its density suddenly decreases. |
| We know that the outer core is a liquid because . . . | S waves can't travel through it |