gcse core physics exam tip: dark, matt surfaces are better emitters & absorbers of thermal...
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GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
KeywordKeyword: : •AbsorberAbsorber•EmitterEmitter•ReflectorReflector
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
Learning Objectives: Identify and explain • Matt black surfaces are the best emitters and absorbers of thermal radiation.• Silver surfaces are the worst emitters and absorbers of thermal radiation.
I will be successful in this lesson if I can: •Use the connectives triangle with literate accuracy.•Use the keywords to ‘bingo’ your work throughout the lesson. •Work together as a team with all members effectively contributing in order to solve a problem (Team work, Effective Participator, Interpersonal)• Describe which surfaces are the best emitters of thermal radiation (Grade C).• Describe which surfaces are the best absorbers of radiation (Grade C).• Explain how the choice of a surface colour can affect the rate of temperature change of an object (Grade A).
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
What colour is a polar bear?
STARTER
WHY?
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
When you go out in the ‘sun’ today, your in for a big surprise….
Use your keywords (bingo) to explain what happens to each women
Use this description Use this description to write a definition to write a definition
for each of the keywordsfor each of the keywords
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
Leslie’s Cube?• To demonstrate that two surfaces at the
same temperature can give off different amounts of thermal radiation. An infra-red sensor can be used to detect levels of IR radiation from the cube.
• The difference is easily felt by placing the back of the hand a few centimetres from the surfaces, but care must be taken that the students do not actually touch the surface.NO not that leslieNO not that leslie
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
How can we test different surfaces for their emission of thermal radiation?
Equipment and materials requiredEquipment and materials required• KettlesKettles• two beakers, two beakers, • two thermometers, two thermometers, • aluminium foil and black card, aluminium foil and black card, • elastic bands (to hold the card on), elastic bands (to hold the card on), • stopclock, stopclock, • a measuring cylinder.a measuring cylinder.DetailsDetails• It is essential to use ‘lids’ on the containers to reduce It is essential to use ‘lids’ on the containers to reduce
evaporation; that thermometers can be poked through to evaporation; that thermometers can be poked through to keep a good seal. keep a good seal.
• Higher starting temperatures give greater temperature drops Higher starting temperatures give greater temperature drops in reasonable times but be extra careful with hot water.in reasonable times but be extra careful with hot water.
In your books;In your books;1)1) Heading; Heading; Investigation on emissionInvestigation on emission
2)2) What are you trying to find out?What are you trying to find out?3)3) Clarify your independent & dependant variableClarify your independent & dependant variable
4)4) Identify what variables will be controlledIdentify what variables will be controlled5)5) Explain how & why they will be controlled Explain how & why they will be controlled
6)6) Draw up a tableDraw up a table7)7) ……then do the experiment….then do the experiment….
In your books;In your books;1)1) Decide which graph to draw from your resultsDecide which graph to draw from your results
2)2) Draw your graphDraw your graph3)3) Identify what you found out be specific byIdentify what you found out be specific by
your independent and dependant variable andyour independent and dependant variable andreferring to actual results referring to actual results
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
Black surfaces (dark, matt colours) are better emitters than white (light, shiny)
surfaces. Explain this by drawing coloured cars
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
PLENARY
• What colour cup would be best to keep orange juice cold on a hot day?
Explain your answer
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
Learning Objectives: Identify and explain • Matt black surfaces are the best emitters and absorbers of thermal radiation.• Silver surfaces are the worst emitters and absorbers of thermal radiation.
I will be successful in this lesson if I can: •Use the connectives triangle with literate accuracy.•Use the keywords to ‘bingo’ your work throughout the lesson. •Work together as a team with all members effectively contributing in order to solve a problem (Team work, Effective Participator, Interpersonal)• Describe which surfaces are the best emitters of thermal radiation (Grade C).• Describe which surfaces are the best absorbers of radiation (Grade C).• Explain how the choice of a surface colour can affect the rate of temperature change of an object (Grade A).
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
Summary notes• Dark, matt surfaces are good absorbers of radiation. An object
painted dull black & left in the sun will become hotter than the same object painted shiny white.
• Dark, matt surfaces are also good emitters of radiation. So an object that is painted dull black will lose heat and cool down quicker than the same object painted shiny white.
• Don’t be fooled by most central heating radiators that are covered in glossy white paint. The best radiators of heat are dark, matt surfaces.
• Remember that an object that is warmer than the surroundings will lose heat and cool down.
• An object that is cooler than the surroundings will gain heat energy and warm up.
• Exam questions will centre around applications of absorption & emission so make sure you understand the difference.
GCSE Core Physics
EXAM TIP: Dark, matt surfaces are better emitters & absorbers of thermal radiation
Check your understandingCheck your understanding
1. Which surfaces are the best emitters of ehat radiation?
2. Which surfaces are the best absorbers of heat radiation?
3. Why are the pipes on the back of a fridge usually painted black?
ANSWERS:
1. The best emitters of heat radiation are dark, matt surfaces.
2. The best absorbers of heat radiation are dark, matt surfaces.
3. To maximise the amount of heat they radiate.
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