P1 1.1 Infrared Radiation

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P1 1.1 Infrared Radiation
Learning Objectives

• Understand what infrared radiation is.
• Know the factors that affect the amount of
  infrared radiation emitted or absorbed by an
  object.
• Explain how infrared radiation can be used.

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Starter Where and how is heat transfer taking
place at this seaside?
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• Barbecue grill cooking burgers and sausages
  (conduction, radiation).
• The car bonnet is so hot that as a sideline to
  the barbecue, someone is cooking food on it
  (conduction).
• Picnic boxes labelled cold and hot contain
  items that have been kept cool and warm,
  respectively, to prevent heat transfer taking
  place.
• The twins on the left are wearing identical
  clothing except that one is wearing a white
  t-shirt and keeping cool, while the other is
  wearing a black t-shirt and looking much hotter
  (radiation).
• The twin in the black t-shirt is trying to keep
  himself cool with a portable fan (convection).
• The fluttering sails on the boat out at sea and
  the fluttering flag on the flagpole show that it
  is windy at the seaside (convection).
• The ice-creams are melted very quickly by the
  heat of the Sun, much to the annoyance of the
  child near the ice-cream van (radiation).

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What does this camera show?
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Transferring energy

• If two objects are at different temperatures e
  will be transferred from the h to the
  cooler object, until they are both the
• s temperature.
• This can happen in different ways
• Infrared radiation
• Conduction
• Convection

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Infrared radiation

• Energy can travel through materials or through
  a vacuum as IR. IR transfers energy by
  waves. Infrared waves are similar to
  waves, except that we
  cannot see them.
• Everything and absorbs IR. The amount
  of IR absorbed or emitted by a body depends on
  its temperature and the nature of its surface.
  

Light, Emits, Electromagnetic, Transparent
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Emitting and absorbing infrared radiation.

• Q) Design a table showing which items of the
  school uniform are good and bad in the summer and
  the winter, with reasons for this?
• A surface will reflect some of the infrared
  radiation that reaches it, and absorb the rest.
• Light coloured, shiny surfaces are good at
  reflecting radiation, so they are poor at
  absorbing it. Dark, matt surfaces are good at
  absorbing radiation.
• Surfaces that are good at absorbing radiation are
  also good at emitting it. Dark matt surfaces are
  good emitters of radiation, and light shiny
  surfaces are poor emitters.

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• http//www.youtube.com/watch?v2--0q0XlQJ0

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1. What is the image?
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2. What is it?
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3. Its a zebra. But in visible light, what
colour are the stripes that look white in
infrared?
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4. What is it?
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5. Why would someone want an infrared image of
their house?
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6. Why does the lizard look so different in
colour from the hand in this infrared picture?
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7. Here you can see infrared waves doing
something that all types of wave can do. What?
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Quick Quiz

1. Do all objects emit infrared radiation?
2. Cross out the incorrect words The
   (hotter/cooler) an object is the (more/ less)
   infrared radiation it radiates in a given time.
3. What kind of surfaces are good emitters of
   infrared radiation?
4. What kind of surfaces are poor emitters of
   infrared radiation?

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Planning an experiment

• Plan a class experiment to
• To measure the temperature of hot water
  cooling in shiny and dark cans.
• Discuss what the independent, dependent and
  controlled variables are.
• What is the fair test for this investigation?
• Make a prediction.
• Draw a labelled diagram of your experiment.
• Write a method to explain what you would do.
• What would you expect to happen?
• Design a results table.

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Copy and complete

• If two objects made from the same material have
  identical v_________, a thin, flat object will
  radiate heat energy faster than a f____ object.
  This is one reason why domestic radiators are
  t______ and flat.
• Radiators are often painted with w_______ gloss
  paint. They would be better at radiating heat if
  they were painted with b______ matt paint, but in
  fact, despite their name, radiators transfer most
  of their heat to a room by c___________.

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Plenary

• Explain why marathon runners are wrapped in foil
  blankets following a race.
• Explain why kettles are light coloured.