There is a lot of emphasis on using Logic at school especially in the later years, to the detriment of Imagination.
As we get older, our imagination dwindles and so we need to actively spend time exercising it.
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
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
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
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