P1A HEATING HOUSES
- The difference between Heat and temperature
- Temperature is represented by colour in a thermogram hottest parts: white/yellow/red; coldest parts: black/dark blue/purple
- Thermal energy(Heat) travels from hot to cold
- Rate of cooling depends on the temperature difference compared to the surroundings.
- Energy in joules (j).
- Energy needed to change the temperature of a body depends on: mass, temperature change.
- (HL)Specific heat capacity
- Energy = specific heat x mass x temperature rise
(HL) Latent heat of vapourisation and melting – all the energy goes into changing the state from solid to liquid rather than increasing the temperature
eg Melting ice cubes, boil water
- Extra energy needed to melt ice but not change the temperature
i.e. no temperature change when materials are boiling, melting or freezing
P1B KEEPING HOMES WARM
- Ways that heat travels through conduction, convection and radiation.
- Trapped air = good insulator.
Infrared radiation is reflected from a shiny surface
- Which materials radiate energy best?
- Sankey diagram – the arrow diagram.
- House insulation by Cavity wall insulation, loft, double glazing, draught excluder
- Pay-back time for different methods of reducing energy loss
- Efficiency = useful energy output divided by total energy input
- Conduction – transfer of kinetic energy between particles, by free electrons
- Convection – when a liquid or gas is heated causes a change of density which results in fluid flow. Radiators
- Radiation – infrared radiation is an electromagnetic wave and needs no medium (air)
P1C A SPECTRUM OF WAVES
- What are waves and how do they behave?
- Frequency, wavelength, amplitude, crest, trough
- Travel in straight lines
- Refraction (bending) at a boundary and diffraction (spreading) of waves at an ‘opening’.
- Transverse, Longitudinal waves
- Speed = frequency x wavelength
- Light waves – Wave or particle
- Reflection at plane mirror and ‘equal angle’ law, ( i = r ).
- Spectrum of light passing through prism.
- Refraction of light rays passing through a rectangular glass block and prism.
- Herschel’s experiment there is an ‘invisible’ radiation beyond the red end of the spectrum.
P1D LIGHT AND LASERS
- Describe the full electromagnetic spectrum
- The use of radio, microwave, infra-red, visible and UV waves in communication.
- Similarities (common speed, able to travel through vacuum) and differences (properties of each related to wavelength and frequency
- Lasers produce an intense coherent beam of light with same frequency,in phase , low divergence.
- Laser beam in a cd player
- Communicating using waves
- Morse Code
- Digital v Analogue
- Refraction of light, critical angle and the optical fibre
- Total internal reflection
- Using of light increased the communication speed but needs a code.
- Laser = light amplification by stimulated emmission of radiation
- Laser is coherent beam of light with waves have the same frequency, in phase,low divergence.
P1E COOKING AND COMMUNICATING USING WAVES
- Cooking with infrared and microwaves (heats water in food).
- Parts of microwave oven: waves are generated (magnetron), the wave guide and the turntable
- Communicating with microwaves (3cm)
- Mobile phone use microwaves.
Diffraction of microwaves
- Scattering of waves by water vapour, large surfaces of water; need for high positioning of transmitter/receiver; loss of line of sight due to curvature of the earth.
- How dangerous are mobile phones?
- Dangers to residents near the site of a mobile phone transmitter mast
P1F DATA TRANSMISSION
- Bar codes
- Infrared sensors detect body heat.
- Using infrared signals in TV controls.
- Analogue signals have a continuously variable value, digital signals are either on (1) or off (0).
- Advantages of digital over analogue, problems of noise in transmission.
- Infrared for photography and security systems.
- Optical fibres – faster internet
P1G WIRELESS SIGNALS
- no external/direct connection to a telephone line needed
- portable and convenient
- allows access when on the move
- but an aerial is needed to pick up the signals.
- Repeater stations and local transmitters on high ground needed for TV (shorter wavelength) but not for radio using longer wavelength.
- ‘Long Wave’ (1500m) stations could be heard across long distances due to diffraction.
Diffraction (ground wave) and refraction leading to total internal reflection in
- ionosphere (skywave) and transmission of very short wavelengths through the atmosphere to reach satellites and return to earth
- The dangers and advantages of wireless technology.
- DAB radio: more stations available; less interference with other broadcasts; poorer audio quality compared to FM;not all areas covered
P1H STABLE EARTH
- What can earthquakes tell us?
- Two types of wave, transverse and longitudinal, and relate these to P and S waves in the earth.
- S waves being unable to travel through liquid, and why P waves (longitudinal) might travel more quickly.
- Should we spend time in the sun?
- Ultra-violet radiation of varying wavelength :
- Helps to form vitamin d in the body
- Overexposure leads to burning,
ultimately can cause skin cancer, cataracts and premature aging
- Darker skin prevents penetration to lower layers.
use of sun-block and sun protection factor (spf).
- What happened to the ozone layer?
Role of CFCs in damaging the layer
- Calculate how long a person can spend in the sun without burning knowing (spf) of sunscreens