Electromagnetic spectrum

What the syllabus asks of you

• Know the main regions of the electromagnetic spectrum in order of frequency and in order of wavelength
• Know that all electromagnetic waves travel at 6 Know that the speed of electromagnetic the same high speed in a vacuum waves in a vacuum is 3.0 × 108 m / s and is approximately the same in air
• Describe typical uses of the different regions of the electromagnetic spectrum including: (a) radio waves; radio and television transmissions, astronomy, radio frequency identification (RFID) (b) microwaves; satellite television, mobile phones (cell phones), microwave ovens (c) infrared; electric grills, short range communications such as remote controllers for televisions, intruder alarms, thermal imaging, optical fibres (d) visible light; vision, photography, illumination (e) ultraviolet; security marking, detecting fake bank notes, sterilising water (f) X-rays; medical scanning, security scanners (g) gamma rays; sterilising food and medical equipment, detection of cancer and its treatment
• Describe the harmful effects on people of excessive exposure to electromagnetic radiation, including: (a) microwaves; internal heating of body cells (b) infrared; skin burns (c) ultraviolet; damage to surface cells and eyes, leading to skin cancer and eye conditions (d) X-rays and gamma rays; mutation or damage to cells in the body continued Core Supplement
• Know that communication with artificial 7 Know that many important systems of satellites is mainly by microwaves: communications rely on electromagnetic (a) some satellite phones use low orbit artificial radiation including: satellites (a) mobile phones (cell phones) and wireless (b) some satellite phones and direct broadcast internet use microwaves because satellite television use geostationary microwaves can penetrate some walls and satellites only require a short aerial for transmission and reception (b) Bluetooth uses radio waves because radio waves pass through walls but the signal is weakened on doing so (c) optical fibres (visible light or infrared) are used for cable television and high-speed broadband because glass is transparent to visible light and some infrared; visible light and short wavelength infrared can carry high rates of data 8 Know the difference between a digital and analogue signal 9 Know that a sound can be transmitted as a digital or analogue signal 10 Explain the benefits of digital signalling including increased rate of transmission of data and increased range due to accurate signal regeneration