CORE OBJECTIVES:

• Know the main regions of the electromagnetic spectrum in order of frequency and in order of wavelength
•  Know that all electromagnetic waves travel at the same high speed in a vacuum
•  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
• Know that 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 satellites

EXTENDED OBJECTIVES:

• Know that the speed of electromagnetic waves in a vacuum is 3.0 × 10⁸m/s and is approximately the same in air.
• Know that many important systems of communications rely on electromagnetic radiation including:
• (a) mobile phones (cell phones) and wireless internet use microwaves because microwaves can penetrate some walls and 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
•  Know the difference between a digital and analogue signal
•  Know that a sound can be transmitted as a digital or analogue signal
•  Explain the benefits of digital signaling including increased rate of transmission of data and increased range due to accurate signal regeneration
• Describe compression and rarefaction
•  Know that, in general, sound travels faster in solids than in liquids and faster in liquids than in gases