describe the main groupings of the electromagnetic spectrum – radio, microwave, infrared, visible (red to violet), ultraviolet, X-rays and gamma rays, that these range from long to short wavelengths, from low to high frequencies, and from low to high energies

recall that our eyes can only detect a very limited range of frequencies in the electromagnetic spectrum

recall that all electromagnetic radiation is transmitted through space with the same very high (but finite) speed

explain, with examples, that electromagnetic radiation transfers energy from source to absorber

recall that different substances may absorb, transmit, or reflect electromagnetic radiation in ways that depend on wavelength

recall that in each atom its electrons are arranged at different distances from the nucleus, that such arrangements may change with absorption or emission of electromagnetic radiation, and that atoms can become ions by loss of outer electrons

recall that changes in molecules, atoms and nuclei can generate and absorb radiations over a wide frequency range, including:

a) gamma rays are emitted from the nuclei of atoms
b) X-rays, ultraviolet and visible light are generated when electrons in atoms lose energy
c) high energy ultraviolet, gamma rays and X-rays have enough energy to cause ionisation when absorbed by some atoms
d) ultraviolet is absorbed by oxygen to produce ozone, which also absorbs ultraviolet, protecting life on Earth
e) infrared is emitted and absorbed by molecules

describe how ultra-violet radiation, X-rays and gamma rays can have hazardous effects, notably on human bodily tissues

give examples of some practical uses of electromagnetic radiation in the radio, microwave, infrared, visible, ultraviolet, X-ray and gamma ray regions of the spectrum

recall that radio waves can be produced by, or can themselves induce, oscillations in electrical circuits