Starter quiz
- Which of the following is not a type of electromagnetic radiation?
- infrared
- light
- sound ✓
- X-rays
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- Which of the following types of electromagnetic radiation are emitted by a hot light bulb?
- infrared ✓
- microwaves
- light ✓
- gamma radiation
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- Surfaces can absorb radiation. Which of the following words or phrases is closest in meaning to the word absorb?
- attract
- fill up
- soak up ✓
- suck in
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- Which of the following statements about infrared radiation are correct?
- It is invisible to human eyes. ✓
- It can be absorbed but not emitted.
- It can be emitted but not absorbed.
- It has higher frequencies than light but lower frequencies than microwaves.
- It has lower frequencies than light but higher frequencies than microwaves. ✓
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- Match up the following key terms about waves with their definitions.
- amplitude⇔The maximum displacement of a wave from the rest position. ✓
- frequency⇔The number of wavelengths passing a point each second. ✓
- oscillation⇔A regular, repeating forwards–and–backwards movement. ✓
- wavelength⇔Distance between two equivalent points on neighbouring wavelengths. ✓
- Which of the following statements about thermal conduction are correct?
- Thermal conduction can happen in a vacuum.
- Metals are particularly good thermal conductors. ✓
- Thermal conduction in a room starts when warmer air rises.
- Thermal conduction happens when energy is transferred by vibrating particles. ✓
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Exit quiz
- A pupil has test tubes of hot water covered in different colours of paper. He investigates whether colour affects the rate of infrared emission. Match each variable with its type in this experiment.
- starting temperature of the water⇔control variable ✓
- temperature drop in a set time interval⇔dependent variable ✓
- colour of paper⇔independent variable ✓
- A pupil has beakers of hot water covered in different colour paper to investigate how colour affects temperature drop caused by infrared energy transfer. Match the parts of her method with the reason.
- same thickness of paper on beakers⇔This variable affects the rate of energy transfer. ✓
- same mass of water in beakers⇔This variable affects temperature change when energy is transferred. ✓
- lids on beakers⇔This reduces energy transfer by evaporation. ✓
- Some objects are better at absorbing electromagnetic radiation than others. An object that absorbs all incident radiation is called a ______. It is theoretical since no object absorbs 100% of radiation.
- 'black body' ✓
- Match the following types of surface to the description of how well it absorbs infrared radiation.
- dull and white⇔sometimes a good and sometimes a poor absorber ✓
- shiny metallic⇔usually a poor absorber ✓
- dull and dark⇔usually a good absorber ✓
- Which of the following statements about absorption and emission of infrared (IR) radiation are correct?
- If a surface is a good absorber of IR radiation, then it is a good emitter. ✓
- If a surface is a good absorber of IR radiation, then it is a poor emitter.
- If a surface is a poor absorber of IR radiation, then it is a good emitter.
- If a surface is a poor absorber of IR radiation, then it is a poor reflector. ✓
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- A metal rod is heated until it glows red. Which of the following statements describe what happens if the rod gets hotter?
- The radiation emitted by the rod transfers more energy per second. ✓
- The wavelength carrying the most energy per second becomes a longer wavelength.
- The range of emitted wavelengths increases to include shorter wavelengths. ✓
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- All bodies (objects) of all temperatures emit and absorb infrared radiation. Hotter bodies emit more IR in a set time.
- The range of wavelengths emitted, and their intensities, depend on an object’s temperature.
- Good absorbers (e.g. dark and dull surfaces) are also good emitters. Shiny metal surfaces are poor absorbers/emitters.
- A black body is a theoretical object that absorbs all of the radiation that falls on it.
- The temperature of a body depends on the rates at which radiation is absorbed and emitted.
Common misconception
White surfaces are always poor absorbers of visible light so they must also always be poor absorbers and emitters of infrared.
White paint is a good absorber and emitter of IR. Colour is not always a good guide to effectiveness at emitting/absorbing IR, except for dark+dull surfaces usually being good emitters/absorbers and shiny metal surfaces being poor emitters/absorbers.
Keywords
Infrared radiation - Infrared radiation means electromagnetic waves with frequencies in a range just lower than for red light.
Emit - To emit infrared radiation is to give out infrared radiation.
Temperature - The temperature of an object measures how hot or cold it is.
Leslie cube - A Leslie cube is a hollow metal cube that can be filled with hot water. Each side has a different colour and finish so emits different intensities of infrared radiation.
Black body - A black body is a theoretical object that absorbs all of the radiation that falls on it.
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