What you’ll learn10 learning objectivesChoose one objective for a focused lesson, or study the complete topic.3.3.1Main regions of the EM spectrum in• Know the main regions of the electromagnetic spectrum in order of frequency and in order of wavelengthSyllabus objective3.3.2All EM waves travel at the same high• Know: all electromagnetic waves travel at the same high speed in a vacuumSyllabus objective3.3.3EM spectrum uses: (a) radio waves• Describe typical EM spectrum uses: (a) radio waves: radio/TV, astronomy, RFID (b) microwaves: satellite TV, mobile phones, microwave ovens (c) infrared: grills, remotes, intruder alarms, thermal imaging, optical fibres (d) visible light: vision, photography, illumination (e) ultraviolet: security marking, fake banknote detection, sterilising water (f) X-rays: medical scans, security scanners (g) gamma rays: sterilising food/medical equipment, cancer detection/treatmentSyllabus objective3.3.4Harm from excessive EM radiation: (a)• Describe harm from excessive EM radiation: (a) microwaves: internal body-cell heating (b) infrared: skin burns (c) ultraviolet: surface-cell/eye damage, skin cancer and eye conditions (d) X-rays/gamma rays: mutation or cell damageSyllabus objective3.3.5Communication with artificial• Know: communication with artificial satellites is mainly by microwaves: (a) some satellite phones use low orbit artificial satellites (b) some satellite phones and direct broadcast satellite television use geostationary satellitesSyllabus objective3.3.6Speed of EM waves in a vacuum is 3.0 ו Know: the speed of electromagnetic waves in a vacuum is 3.0 × 108 m/s and is approximately the same in airSyllabus objective3.3.7EM radiation: (a) mobile• Know communication systems using EM radiation: (a) mobile phones/wireless internet use microwaves because they penetrate some walls and need short aerials (b) Bluetooth uses radio waves because they pass through walls but weaken (c) optical fibres use visible/infrared for cable TV and high-speed broadband because glass transmits them and they carry high data ratesSyllabus objective3.3.8Difference between a digital and• Know the difference between a digital and analogue signalSyllabus objective3.3.9A sound can be transmitted as a• Know: a sound can be transmitted as a digital or analogue signalSyllabus objective3.3.10Benefits of digital signalling• Explain the benefits of digital signalling including increased rate of transmission of data and increased range due to accurate signal regenerationSyllabus objective