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Teachers Guide for Radiation beyond Visible Spectrum
"By Exploring Radiations Beyond the visible, I can describe a selected application, discussing the advantages and limitations. SCN 3-11b"
Background Science (Covered in Previous Lessons)
Definition of frequency: The number of wave peaks that pass a fixed point in one second. Measured in Hertz (Hz).
Definition of wavelength: The distance from a point on one wave to the corresponding point on the next wave. Measured in metres (m), or more commonly nanometres (nm).
Our eyes are only capable of detecting wavelengths of light between a certain range; this is called the visible spectrum and is what allows us to see colours. Beyond the visible spectrum there are named wavelengths which we cannot see but can be detected by some animals & machines. This lesson will look at Infra-red and we will consider uses of such radiation.
For this particular lesson you can focus on infra-red radiation as an example. Infra-red radiation is emitted by heated objects. Get the students to note down different materials that they can find, e.g. marble, granite, stone, wood, metal. Ask them to touch each material and note down how hot it is, they can then compare which materials are hotter than others. You can then use a thermal imaging camera and point it at the materials. The hot objects will be red or orange, cold objects will be black or blue. The students will then be able to link infra-red radiation to heat and see that some objects conduct heat better than others. They can then also take photographs of themselves with the camera and try to point out which bits of their own bodies are hotter/colder than the rest and why.
Learning for Sustainability
This lesson can be linked to learning for sustainability. Thermal imaging of the Earth can show effects of global warming, e.g. melting of polar ice caps, which explains rising sea levels. It can also show thermal heat currents in the sea & areas of desert which are getting hotter every year. Showing the students these thermal pictures can help them point out differences in hot and cold places over a long period of time. It can also lead to discussion on effects of global warming and climate change, which links to knowledge of fossil fuels earlier in their science education.
Cross Curricular Links
This learning outcome can be linked to other school subjects and provide useful classroom discussion.
Biology: Icecaps melting means that animals such as polar bears and penguins will die out, this means that animals which prey on them, such as whales, will be effected. As such this will be a huge impact on the food chain. Sea temperatures experiencing a drastic change will lead to sea animals travelling to places they haven’t before which also interferes with the food chain. It can also be dangerous for animals and people when predators start to move inland towards population centres.
Infra-red radiation can also be used medically to detect tumours in the body in a non-invasive way.
Geography: Rising sea levels & desertification will lead to many areas becoming uninhabitable, as such there will be a population movement which may result in an overcrowding of cities. This overcrowding will have an impact on the education system and the health care system.
Vocabulary: Infra means ‘further on’. Therefore it can be explained to the students that 'infra-red' translates to further on past red. This can be demonstrated to the students by showing them that infra-red is just beyond red in the light spectrum. This can then also be used to explain the differences in wavelength and frequency compared to red light.