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Year 9 Electromagnetic Spectrum
Students should understand the following:
- Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber.
- Electromagnetic waves form a continuous spectrum and all types of electromagnetic wave travel at the same velocity through a vacuum (space) or air.
- The waves that form the electromagnetic spectrum are grouped in terms of their wavelength and their frequency. Going from long to short wavelength (or from low to high frequency) the groups are: radio, microwave, infrared, visible light (red to violet), ultraviolet, X-rays and gamma rays.
- Our eyes only detect visible light and so detect a limited range of electromagnetic waves.
- Students should be able to give examples that illustrate the transfer of energy by electromagnetic waves.
- Radio waves can be produced by oscillations in electrical circuits.
- When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself, so radio waves can themselves induce oscillations in an electrical circuit.
- Changes in atoms and the nuclei of atoms can result in electromagnetic waves being generated or absorbed over a wide frequency range. Gamma rays originate from changes in the nucleus of an atom.
- Ultraviolet waves, X-rays and gamma rays can have hazardous effects on human body tissue. The effects depend on the type of radiation and the size of the dose.
- Students should be able to draw conclusions from given data about the risks and consequences of exposure to radiation.
- Ultraviolet waves can cause skin to age prematurely and increase the risk of skin cancer. X-rays and gamma rays are ionising radiation that can cause the mutation of genes and cancer.
- Electromagnetic waves have many practical applications. For example:
- radio waves – television and radio
- microwaves – satellite communications, cooking food
- infrared – electrical heaters, cooking food, infrared cameras
- visible light – fibre optic communications
- ultraviolet – energy efficient lamps, sun tanning
- X-rays and gamma rays – medical imaging and treatments.
- Students should be able to give brief explanations why each type of electromagnetic wave is suitable for the practical application.
LOGON SCIENCE codes: 18.104.22.168, 22.214.171.124, 126.96.36.199, 188.8.131.52, 184.108.40.206, 220.127.116.11
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