Physics Unit 1

  • Created by: YOIMO
  • Created on: 23-05-17 18:29

P1.1 Part 1

  • all objects emit infrared radiation
  • infrared radiation can travel through space ie the sun
  • dark, matt surfaces are good absorbers and emitters of radiation
  • if one end of a solid is heated: gain kinetic energy and vibrate more, energy is passed on through the solid
  • when a metal is heated their free electrons gain kinetic energy and move through the metal, transferring energy by colliding with other particles
  • when a fluid is heated, it expands, becomes less dense and rises resulting in convection currents. the warm fluid is replaced by cooler, denser fluid
  • rate of evaporation is increased by: increasing surface area, increasing temp, draught of air across liquids surface
  • condensation is when a gas turns into a liquid
  • rate of condensation is increased by: increasing surface area, reducing surface temp
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P1.1 Part 2

  • rate at which energy is transferred: materials the object is in contact with, objects shape, objects surface area
  • maximise the rate of energy transfer to keep things cool by: good conductors, painted dull black have the air flow around them maximised
  • minimise the rate of energy transfer to keep things warm by: good insulators, white and shiny, prevent convection currents by trapping air in small pockets
  • vacuum prevents convection and conduction
  • minimise heat transfer by fitting: loft insulation from conduction, cavity wall insulation from convection as air pockets trap air, double glazing from conduction, draught proofing from convection, aluminium foil behind radiators to reflect infrared radiation back into the room
  • U-value of a material tells us how much energy per second passes through it. the lower U-value is better
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  • Types of energy: SICK HEN LEG: Sound Infrared-radiation Chemical Kinetic,  Heat Elastic Nuclear, Light Electrical Gravitational-potential
  • a falling object transfers gravitational potential to kinetic energy
  • stretching an elastic band transfers chemical energy into elastic potential energy
  • in a solar cell, light energy is transferred to electrical energy
  • a swinging pendulum transfers energy from gravitational energy to kinetic energy
  • energy is measured in joules J
  • unit of power is the watt W, 1000W = 1KW
  • cost effectiveness: buying, installing, running, maintenance, environmental, interest on loan of money
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  • nuclear power stations use uranium or sometimes plutonium
  • the nucleus of the uranium atom has the process of nuclear fission wich releases energy
  • there are lots of uranium nuclei, so lots of fission reactions take place and lots of energy is produced
  • steam turns turbine, turns generator
  • renewable energy- never used up
  • solar energy from the sun travels through space to the earth as electromagnetic radiation. solar cell transfers energy into electrical energy
  • geothermal energy uses the heated rocks around which is from radioactive decay
  • coal and oil produce acid rain
  • power station then has a step-up transformer because the high voltage reduces the energy wasted in the cables, making the system more efficient
  • base load- constant amount of electricity generated by power stations
  • household energy is 230V
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P1.5 Part 1

  • use waves to transfer energy and information
  • ET transverse waves vibrate at right angles to the direction of energy transfer. all electromagnetic waves are transverse waves
  • LS longitudinal waves vibrate parallel to the direction of energy transfer. a sound wave is longitudinal. made up of compressions and rarefactions
  • electromagnetic waves eg. light waves and radio waves can travel through a vacuum. there are no particles moving in an electromagnetic wave, as these waves are oscillations in electric and magnetic fields
  • mechanical waves eg springs and sound waves travel through a medium. may be transverse or longitudinal
  • sound waves are longitudinal
  • amplitude- half of wave height
  • the greater the amplitude, the more energy it carries
  • frequency is the number of waves per second in Hz
  • frequency of a longitudinal wave is the number of compressions passing through a point per second
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P1.5 Part 2

  • the image in the mirror is: the same size as object, upright, same distance behind the mirror as the object is in front, virtual
  • real image- an image formed where light rays meet
  • virtual image- an imaged formed where light rays appear to meet
  • when a light enters a more dense substance, such as going from air to glass, it slows down and the ray changes direction towards the normal
  • if less dense then it moves away from the normal
  • when a white light is shone onto a triangular glass prism, the light refracts to see the spectrum. this is called dispersion
  • violet refracts the most and red refracts the least
  • diffraction is the spreading of waves when they pass through a gap or around an edge of an obstacle
  • the narrower the gap, the greater the diffraction
  • all waves are diffracted
  • the wavelength of light is very short therefore we don't observe it
  • sound waves travel quickest in solids rather than gases
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P1.5 Part 3

  • sound can't travel through a vacuum eg space
  • sound waves are longitudinal
  • human ears range is 20hz-20,000hz
  • sound waves can be reflected to produce echoes: only hard and flat surfaces, soft things like carpets and curtains absorb sound, empty rooms sound different
  • sound waves can be refracted were the refraction takes place at the boundaries between layers of air at different temperatures
  • sound waves can also be diffracted
  • the pitch of a note depends on the frequency of the waves. higher the frequency, the higher the pitch
  • loudness depends on the amplitude
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P1.6 Part 1

  • all electromagnetic waves travel through a vacuum at the same speed but they have different wavelengths and frequencies
  • gamma rays- shortest wavelength, highest frequency- 10(-15)m
  • radio waves- longest wavelength, lowest frequency- 10,000m+
  • the higher the frequency, the higher the energy it transfers
  • Radio, Microwaves, Infrared, Light, Ultraviolet radiation, X-rays and Gamma radiation. RMILUXG = RoMania Is LUXembourG      Romania is a bigger country so it has bigger wavelengths but a lower frequency as not as many people per area
  • TV remotes use infrared radiation (IR)
  • microwave radiation and radio waves penetrate through the skin and are absorbed by body tissue. can lead to heating internal organs and may damage them. too much infrared radiation burns the skin
  • an alternating voltage applied to an aerial emits radiowaves with the same frequency as the alternating voltage. the waves received then produce alternating current in the aerial with same frequency as radiation received
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P1.6 Part 2

  • the shorter the wavelength of the waves the more information they carry, the shorter their range, the less they spread out
  • some scientists believe the radiation from mobile phones affects the brain, particularly children
  • optical fibres transmit visible light or infrared radiation through very thin glass fibres. the signals travel down the fibre by repeated total internal reflection. useful in carrying more information and are more secure than radio waves
  • when the source moves away from the observer, the observed wavelength increases and the frequency decreases. alternate if it moves towards you
  • doppler effect example is an ambulance siren, moving away from you is a lower pitch, moving towards you is a higher pitch
  • galaxies are large collections of stars. light observed from distant galaxies has been 'shifted' towards the red end of the spectrum. this is known as red-shift and means that the frequency has decreased and the wavelength increased
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P1.6 Part 3

  • a blue-shift would indicate that a galaxy is moving towards us. we are able to see these effects by observing dark lines in the spectra from galaxies
  • the further away the galaxy, the bigger the red-shift suggesting distant galaxies are moving away from us, the most distant galaxies are moving the fastest- true of all galaxies
  • all the distant galaxies are moving away from each other, so the whole universe is expanding
  • if it is expanding then it must have started with a massive explosion at a very small initial spot AKA Big Bang
  • high energy gamma radiation would have been produced from Big Bang. as the universe expanded, this would have become lower energy radiation
  • cosmic microwave background radiation (CMBR) is electromagnetic radiation created just after the Big Bang- Big Bang is only proof of CMBR
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