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house heating
- Temperature is a measure of how hot something is
  - An object that is 50c above room temperature cools quicker than an object 5c above room temperature
  - Measured in degree celsius, heat is a measurement of energy. The unit of energy is he joule (j)
  - Heat travels from a warmer body to a cooler body.
    - The warmer body becomes cooler as energy is flowing away
  - Thermograms measure temperature using colour as a scale
  - The particles in a substance are constantly vibrating. temperature is a measurement of the average kinetic energy of the particles
- The amount of energy needed to heat a liquid depends on: The mass of the liquid being heated. The temperature increase. The type of object or liquid
  - can be measured using an electrical immersion heater connected to a joulemeter
  - Specific heat capacity
    - All objects have a property called their SHC (the amount of energy needed to change the temperature of one kilogram of a substance by one degree celsius)
    - SHC is joule per kilogram degree celsius (j/kgoC)
    - Energy transferred= mass x shc x temperature change
- If you heat a solid, its temperature rises until its melting where the temperature doesn't increase until all the solid has melted. The same occurs when changing to a gas state
  - Heat is needed to melt an object at its melting point, heat is needed to make an object boil a its boiling point
  - Latent heat is the heat needed to change state without changing temperature
    - All substances have a property called Specific Latent heat (The amount of energy needed to change the state of one kilogram of a substance without a change in temperature)
      - Joule per kilogram (J/kg)
      - energy tranferred = Mass x SLH
  - When a substance is changing state from solid to liquid or liquid to gas energy is needed to break bonds that hold the molecules together, that's why there is no temperature change
Keeping homes warm
- Energy transfer
  - Insulation
    - Air is a good insulator
  - Conduction
    - Whenever something is heated then the particles vibrate more quickly.
      - Solids conduct better as they are more closely packed
        Gases are poor conductors as particles are distant from eachother. vacuums contain no particles so there is no conduction
        Metals are the best conductors. Delocalised Electrons in the metal can also transfer heat energy as they can increase the kinetic energy by colliding with other atoms (ions)
  - Infrared radiation is absorbed by dull, rough black surfaces and reflected by shiny silver surfaces: why solar heaters are pained black
    - Infrared is an EM wave so can transfer energy without material such as why it travels through the empty space and its emptyness
  - Convection
    - When a gas is heated its density decreases and it expands causing hot gas particles to rise. Density : g/cm3 or kg/m3
      - Air is a good insulator but its also a good convector. air in a cavity forms a convection current. trapped air in the cavity insulation stops convection from occuring
        Only fluids can cause convection as they flow
        less dense gas particles rise and distribute energy then the cool particles drop down as they cool
- house insulation.
  - Double glazed windows have a space between the panes. the space is filled with air, argon or a vacuum
    - Vacuum is the best insulator
    - closing curtains also save energy transfer in the window
  - Foam cavity wall insulation contains lots of trapped air. this reduces conduction
  - Building blocks in new houses have foil wrapped either side of each block. so in the winter heat is reflected back and summer heat is reflected out
  - Warm air rises so when it reaches he loft the heat is lost to conduction.
    - If there is no insulation then convection currents can emerge in the roof. if there is insulation particles cant move around
- Sankey diagrams
- Payback time: Cost/ Annual saving
- When energy is lost its known as a "Source" to "sink". The method are to prevent Convection, Conduction, and radiation
Spectrum of waves
- Transverse waves
  - All transverse waves share the same features
    - Amplitude is the maximum disturbance cause by the wave at a trough or crest from the normal line.
      - Wavelength: is the distance between corresponding points on two successive disturbances (peak to peak)
        Frequency is the number of waves produced past a point in one second
  - Longitudinal
- EM spec
  - All travel in straight lines at 300,000,000 m/s. all transverse wave with different frequencys and wave length
    - The EM waves are used for communication and he size of the wavelength have to be similar to the reciever
      - Sateliite dishes have small receivers to detect microwaves
  - Gate X Usually Lets In Most Radiation. Gamma X-ray UV Light Infrared Microwaves Radio waves
  - Visible light and infrared use optical fibres to communicate
    - Morse code: Communicating with light is by far the fastest way to. morse code is a series of dots and dashes to write a word. these messages were relayed by stations to increase distance
    - Multiplexing: Optical fibres can have multiple messages sent through as the light can be sen in different wavelengths (colours)
Reflection
- When a ray of light hits a shiny surface it is reflected
  - The Incident angle = Reflection angle
    - Multiple reflections mean light can reflect off a series of surfaces
- Refraction
  - Usually when a ray of light or infrared passes from one material into another and changes direction. this happens because the waves change speed
  - Diffraction: is when a wave spreads after going through a narrow opening
    - Can also occur when a wave passes an obstacle. if the obstacle is large then the wavelength has to be large otherwise here is no effect
    - If the gap is a similiar size or smaller he diffraction if high but if i is much larger then it is no as noticable
    - Wave based sensors such as telescopes or optical microscopes have issues with diffraction. two stars may diffract and act as one