Infrared Radiation

  • Created by: Georgia
  • Created on: 01-12-17 16:57
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  • Energy Transfer by heating
    • Energy Transfer by Heating
      • Thermal conductor = material that allows thermal energy to pass through
      • Thermal insulator = material that doesn't allow thermal energy to pass through
      • Rate of thermal energy transfer depends on:
        • The temperature difference
        • The thickness of the material
        • The thermal conductivity of the material
      • To reduce the rate:
        • have as low a thermal conductivity of the material as possible
        • The material should be as thick as possible
    • Infrared radiation
      • Part of the electromagnetic spectrum
      • Makes us feel hot
      • All objects give this off
      • An object at a constant temperature emits the same amount as it absorbs
      • An object that is getting hotter emits more radiation than it absorbs
      • An object that is getting colder absorbs more than it emits
      • An object with a light/shiny surface will absorb and emit less radiation than one with a dark/matt one
    • Greenhouse Effect
      • Earth receives infrared radiation from the sun
      • Radiation from the sun is absorbed by the Earth's ground or atmosphere
      • Some of the radiation is reflected by the ground but gets trapped by the gases in the air
        • This is because the radiation is reflected at a shorter wavelength
        • This causes the atmosphere to gradually heat up
        • This is the greenhouse effect
    • Specific Heat Capacity
      • The amount energy needed to heat 1 kg of a substance 1C
      • The higher it is, the more energy needed
      • A greater mass requires more energy
      • Calculating energy required to change the temp of a substance
        • Energy = mass x s.h.c x temperature change
          • mass measure in kg
    • Heating and insulating buildings
      • People want to reduce the amount of heat lost from their houses
      • Fiberglass roof insulation
      • Cavity wall insulation
      • Aluminium foil behind radiators
        • Reflects infrared radiation back into the room
      • Double glazing around the windows
      • Thick bricks with low thermal conductivity
      • Solar Panels
        • Absorb infrared radiation from the sun
        • Cells generate electricity directly
        • HEating panels heat water directly
    • Perfect Black bodies
      • Absorbs all the radiation that hist them
      • Best possible emitter of radiation
      • Radiation from them is clled black body radiation

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