Karteikarten
6. Waves
Karten in diesem Stapel (88)
- 1What is a wave?A wave is an oscillation that transfers energy without transferring matter by making the particles of a substance oscillate.
- 2What direction do transverse waves oscillate in comparison to the direction they travel in?Transverse waves oscillate at a right angle to the direction they travel in.
- 3What direction do longitudinal waves oscillate in comparison to the direction they travel in?Longitudinal waves oscillate along the same line as the direction they travel in.
- 4What specific type of waves are an example of transverse waves?Electromagnetic waves are transverse.
- 5What specific type of waves are an example of longitudinal waves?Sound waves are longitudinal.
- 6What are the areas of compression and the areas of spreading called in a longitudinal wave?Compressions and rarefactions.
- 7Do waves move matter particles when they travel through a medium and why?No, waves do not transfer matter, only energy between particles within matter e.g. a ripple on water does not move twigs on the surface.
- 8What is the amplitude of a wave?The amplitude of a wave is the maximum displacement from a point's undisturbed position, or the distance from this central position to a crest or trough.
- 9What is the wavelength of a wave?The wavelength is the distance between the same point on two adjacent waves.
- 10What is the frequency of a wave and its units?The frequency of a wave is the number of complete waves passing a point per second. It is measured in Hertz (Hz).
- 11What is the period of a wave?The period of a wave is the time it takes for one full cycle of the wave to be completed.
- 12Wave speed = ?Wave speed = wavelength x frequency
- 13How do you measure the speed of sound in air?1. Generate a sound wave with a specific frequency by attaching a signal generator to a speaker, which will be detected by microphones which convert it onto an oscilloscope.
2. Slowly move one microphone away from the speaker until the waves are aligned on the oscilloscope.
3. Measure the distance between them to find the wavelength. - 14What can happen when a wave hits a boundary?- Absorption - The energy is transferred to the materials energy stores.
- Reflection - The waves bounce back.
- Transmission - The wave travels through the material and often undergo refraction. - 15What is the normal?The normal is a straight line at 90º to the edge of a material shown with a dotted line.
- 16What is the incident ray and the angle of incidence?The incident ray is the incoming wave that meets the normal at the boundary. The angle of incidence is the angle at which this happens.
- 17What is refraction?Refraction is the deflection of a wave as it passes into a substance of a different density.
- 18What changes and what remains the same during refraction?In refraction, the speed of the wave changes but the frequency remains the same.
- 19What is the optical density of a material?The optical density is a measure of how quickly light travels through it - the higher the optical density, the slower the light travels.
- 20What are wavefronts?Wavefronts are imaginary lines drawn through certain points on waves that are perpendicular to the direction that the wave is moving.
- 21Which way does a wave bend if it slows down at a boundary or speeds up?If it slows down, the wave bends towards the normal, and if it speeds up, the wave bends away from it.
- 22What is the angle of incidence?The angle of incidence is the angle between the incoming wave and the normal.
- 23What is the law of reflection?The angle of incidence = the angle of reflection.
- 24What is specular reflection?Specular reflection is when parallel waves are reflected in a single direction by a smooth surface.
- 25What is diffuse reflection?Diffuse reflection is when parallel waves are reflected by a rough surface and are scattered in lots of directions.
- 26What are electromagnetic waves?EM waves are those consisting of vibrating electric and magnetic fields.
- 27What are the types of EM waves in order of increasing frequency?- Radio waves
- Microwaves
- Infra red
- Visible light
-Ultraviolet
- X-rays
- Gamma rays - 28How are EM waves produced inside atoms?When energy is absorbed by an atom, some of the electrons move to higher energy levels, then when each falls back down this energy is released as an EM wave.
- 29How does the energy of an EM wave relate to its frequency?The higher the energy a wave transfers, the higher the frequency.
- 30How can radio waves be produced?Radio waves can be produced using an alternating current (ac) in an electrical circuit. As the charges oscillate, they produce oscillating electric and magnetic fields aka EM waves. The frequency of the waves is equal to that of the current.
- 31What is the object in which charges oscillate to create the radio waves called?A transmitter.
- 32How are radio waves received?When transmitted radio waves reach a receiver, the radio waves are absorbed and the energy is transmitted to the kinetic energy stores of the electrons in the receiver material. This causes them to oscillate and generate an alternating current if it is part of a complete circuit.
- 33What can long-wave radio signals do?Long-wave radio signals can be transmitted halfway round the world because long wavelengths diffract (bend) around the curved surface of the Earth and around obstacles.
- 34What can short-wave radio signals do, and what other type of signals can also do this under what conditions?Short-wave radio signals cannot diffract (bend) around the Earth's surface but are reflected between the Earth and the ionosphere. Medium-wave signals can also do this depending on atmospheric conditions and time of day.
- 35What is the ionosphere?The ionosphere is an electrically charged layer in the Earth's upper atmosphere.
- 36What type of waves are used for TV signals and FM radio and why?Very short-wave radio signals are used so you have to be in direct sight of a transmitter to get reception.
- 37What type of waves are used for satellite communications and how?Microwaves are used because certain wavelengths can pass easily through the Earth's atmosphere. The signal is transmitted into space, picked up by the satellite's receiver and then transmitted in a different direction to a satellite receiver back on Earth.
- 38How do microwave ovens work?These microwaves have wavelengths that allow them to be absorbed by food's water molecules and transfer their energy to the molecules' thermal energy store, which is then transferred to the rest of the food molecules.
- 39How do infrared cameras work?Infrared cameras can be used to detect infrared radiation and turn it into an electrical signal that is displayed on a screen. The higher an object's temperature, the more IR radiation it emits.
- 40How do electric heaters work?A long piece of wire heats up when a current flows through it and this energy is transferred by infrared waves to the thermal energy stores of surrounding objects and air.
- 41What type of waves are used for fibre optic cables and how?Visible light is pulsed through an optical fibre, a thin glass or plastic fibre that can carry data, and is reflected off the walls back and forth until it reaches the end. It will travel down the fibre without being absorbed or scattered much, so the signal hardly weakens at all.
- 42How does security ink work?When UV radiation hits certain chemicals, it is absorbed and visible light is emitted; this is called fluorescence. Security pens can mark valuable items with ink containing these chemicals so stolen property can be identified and banknotes use it as a security feature.
- 43What type of waves are used for energy efficient lamps and how?Fluorescent lamps use ultraviolet rays as they have glass tubes coated with fluorescent chemicals and filled with a mixture of mercury and noble gases. The UV waves are emitted by mercury atoms when an electrical current is switched on.
- 44How does medical imaging work?X-rays are directed through a patient towards a detector plate which forms a negative image as they pass easily through flesh but not so easily through denser material like bone or metal.
- 45What type of waves are used as medical tracers and why?Gamma rays emitted by a gamma-emitting isotope are used because they will not do any damage as they can easily pass through the body, which also allows them to be detected easily.
- 46Which types of EM radiation are most damaging and why?High frequency waves such as gamma, X-rays and UV waves are most damaging because they all transfer lots of energy.
- 47What harm can certain types of radiation cause?UV rays damage surface cells, which can cause sunburn, premature ageing, blindness and an increased risk of skin cancer. X-rays and gamma rays are types of ionising radiation that carry enough energy to knock electrons off atoms, so they can kill cells or cause gene mutations.
- 48What is radiation dose and its units?Radiation dose is a measure of the risk of harm from the body being exposed to radiation. It takes into account the total amount of radiation, how harmful the type is and the type of tissue absorbing it. It is measured in sieverts.
- 49What are the rough average wavelengths of violet and red light?Violet = around 400nm
Red = around 700nm - 50What types of objects transmit light and how, and which do not?Transparent objects transmit light in straight lines so you can see clearly through them and translucent objects transmit light but also scatter it so you can't see through clearly, and opaque objects cannot transmit light.
- 51What defines the apparent colour of an object?The colour of an object is defined by the wavelengths of light it reflects, which can be either those of the light of its colour or those of the light in the primary colours that compose it. All other colours of light are absorbed.
- 52Why can objects appear white or black?White objects reflect all colours of light whereas black objects absorb all colours.
- 53What do colour filters do?Colour filters only transmit certain wavelengths and absorb all others.
- 54What are the effects of colour filters on objects?If the filter is for a primary colour, objects that reflect the same wavelengths will appear that colour. If it is not then objects containing any of the included primary colours will reflect each of those wavelengths. For each, objects that do not apply will appear black.
- 55Which objects absorb and emit infrared radiation, and what affects how much?All objects are constantly emitting and absorbing infrared radiation, and the hotter an object is, the more it emits in a given time.
- 56Why does an object with a different temperature to its environment cool down or heat up?An object hotter than its surroundings emits more radiation than it absorbs so its temperature falls, and vice versa.
- 57Which surfaces are the best and worst at absorbing and emitting infrared radiation?Black or matt surfaces are best at absorbing and emitting radiation and white or shiny surfaces are worst.
- 58What happens to solar radiation on Earth?Some solar radiation is reflected by the atmosphere, clouds or bright surfaces e.g. snow and the rest is absorbed by the atmosphere or the Earth's surface, which is then emitted as infrared.
- 59How does radiation affect the Earth's overall temperature?During the day, more radiation is absorbed than emitted so the temperature increases and at night the opposite occurs. As a result, the temperatures of the Earth's surface and atmosphere stay fairly constant overall.
- 60What is a perfect black body?A perfect black body is an object that absorbs all electromagnetic radiation that hits it, and only exist theoretically in the context of everyday life.
- 61How does an object's temperature affect the intensity of its emitted radiation?The intensity of every emitted wavelength increases as temperature increases.
- 62What is the intensity of a wavelength?Intensity is the power per unit area, or energy transferred to a given area in a set time.
- 63How does an object's temperature affect the peak wavelength of its emitted radiation?The peak wavelength of an objects emitted radiation decreases as temperature increases.
- 64What are convex and concave lenses?Convex lenses bulge outwards (a converging lens) and concave lenses cave inwards (a diverging lens).
- 65What is the principal focus of a lens?The principal focus of a lens is where rays hitting the lens parallel to the axis meet or appear to come from.
- 66What is the focal length?The focal length is the distance between the centre of the lens and the principal focus.
- 67What must be draw on a ray diagram?- Lens symbol
- Axis (horizontal)
- Rays
- Arrows
- Principal focus
- Image - 68What are the rules for incident rays travelling through convex lenses?An incident ray...
- Travelling parallel to the axis will then pass through the principal focus.
- Passing through the principal focus before the lens will then travel parallel to the axis.
- Passing through the centre of the lens will continue the same. - 69What are the rules for incident rays travelling through concave lenses?An incident ray...
- Travelling parallel to the axis will then travel in line with the near-side principal focus.
- Passing towards the far-side principal focus before the lens will then travel parallel to the axis.
- Passing through the centre of the lens will continue the same. - 70What is a real image?A real image is that formed when light rays from a point on an object meet after passing through the lens and can be captured on a 'screen', such as that on an eye's retina.
- 71What is a virtual image?A virtual image is formed when the light rays from a point on an object diverge after passing through the lens and the light from a point on the object appears to be coming from a different place, such in the use of a magnifying glass.
- 72What do convex and concave lens symbols look like?Convex symbols are a double-ended arrow, concave symbols are a line with an inverted arrow coming from either end.
- 73How do you draw an image on a ray diagram?A real image will be from the axis to the point where the rays meet and a virtual image will be from the axis to the point where rays traced back from the lens appear to meet.
- 74How do magnifying glasses work?Magnifying glasses use convex lenses and create a virtual, upright image that is magnified and on the same side as the object.
- 75Through matter in what state do sound waves travel faster and why?Sound travels faster in solids because the molecules are closer and it takes less time to pass the sound between them.
- 76What happens to a sound wave when it enters a denser material?The wave speed and wavelength increase but the frequency stays the same.
- 77How do sound waves travel through solids?The air particles hitting the object cause the closest particles to vibrate. These hit the next particles along and this process continues.
- 78What happens when a sound wave enters the ear?Sound waves of certain frequencies hit the eardrum and cause it to vibrate, then these are transferred to tiny bones known as ossicles, through the semicircular canals and to the cochlea. The vibrations are then turned into electrical signals.
- 79What is ultrasound?Ultrasound waves are sound waves with frequencies greater than 20kHz and cannot be heard by humans.
- 80What are the properties of ultrasound?d
- 81What is partial reflection?Partial reflection is where some of the waves are reflected by the boundary between two media and some are transmitted or possibly refracted.
- 82How can ultrasound be used to detect how far away a boundary is?The time it takes the ultrasound waves to reach a detector, similar to an echo, shows how far away the boundary is.
- 83How can ultrasound be used in medical imaging?Ultrasound waves can pass through the body, but when they reach a boundary between two different media e.g. fluid in the womb and the foetus, some is reflected back and detected. The timing and distribution of the echoes allow the computer to produce an image.
- 84How can ultrasound be used in industrial imaging?Ultrasound waves can be used to find flaws in objects such as pipes as they are usually reflected by the far side of the material, and a flaw will cause the wave to be detected sooner.
- 85How does echo sounding work?High-frequency sound waves are used in some boat and submarine sonars to calculate the distance to an object by the time taken for it to be detected.
- 86What are seismic waves?Seismic waves are those that travel out through or accross the Earth's surface.
- 87What are the differences between P-waves and S-waves?P-waves are longitudinal seismic waves that can travel through solids and liquids, whereas S-waves are transverse, always travel slower than P-waves and can only travel through solids.
- 88How can seismologists build up a picture of the paths of seismic waves from the epicentre?The waves are measured my seismometers at various points, and usually as the density of the Earth's surface gradually changes so does the speed, which as it decreases causes a slightly curved path. If the medium the waves travel through suddenly changes, the path will have a kink.
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- GCSE Physics Karteikarten am 6. Waves , erstellt von JR HN am 18/12/2018.
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