What is the electromagnetic spectrum?
A continuous range of electromagnetic waves arranged in order of wavelength or frequency.
What are the 7 main regions of the EM spectrum (longest wavelength → shortest)?
Radio waves → Microwaves → Infrared → Visible light → Ultraviolet → X-rays → Gamma rays.
What happens to wavelength and frequency across the EM spectrum?
As wavelength decreases, frequency increases.
What do all electromagnetic waves have in common?
They are transverse waves.
They transfer energy.
They travel at the same speed in a vacuum (≈ 3 × 10⁸ m/s).
What are radio waves used for?
Broadcasting (TV, radio), communications.
What are microwaves used for?
Satellite communication, mobile phones, and cooking (microwave ovens).
What are infrared waves used for?
Heaters, night-vision cameras, remote controls, thermal imaging.
What are visible light waves used for?
Seeing things, photography, fibre optic communication.
What are ultraviolet (UV) waves used for?
Detecting forged banknotes, fluorescent lamps, sterilising equipment.
What are X-rays used for?
Medical imaging (bones), security scanning.
What are gamma rays used for?
Sterilising medical equipment, treating cancer (radiotherapy).
What are the dangers of microwaves?
Can heat internal body tissue and cause burns.
What are the dangers of infrared radiation?
Can cause skin burns.
What are the dangers of ultraviolet radiation?
Can cause skin damage, sunburn, and increase risk of skin cancer.
What are the dangers of X-rays and gamma rays?
Ionising radiation — can damage or kill cells, cause mutations and cancer.
What does “ionising radiation” mean?
Radiation with enough energy to remove electrons from atoms, forming ions.
How are radio waves produced?
By oscillating (alternating) electric currents in an electrical circuit (antenna).
How are radio waves detected?
They induce an alternating current in a receiver antenna.
How can electromagnetic waves be generated or absorbed?
When electrons or atomic nuclei lose or gain energy.
How are EM waves different in materials compared to a vacuum?
Their speed changes depending on the medium (e.g. slower in glass than air).
What part of the EM spectrum can the human eye detect?
Visible light — wavelengths approximately 400 nm to 700 nm.
What determines the energy of an EM wave?
Its frequency — higher frequency means higher energy.
