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ELECTROMAGNETIC SPECTRUM Chapter 13 LEARNING OBJECTIVES • State that all electromagnetic waves are transverse waves that travel with the same speed in vacuum and state the magnitude of this speed. • Describe the main components of the electromagnetic spectrum. LEARNING OBJECTIVES • State examples of the use of the following components: • radio waves(eg. radio and television communication) • microwaves(eg. microwave oven and satellite television) • infra-red(eg. infra-red controllers and intruder alarms) • light(eg. optical fibres fro medical uses and telecommunications) • ultra-violet(eg. sunbeds and sterilisation) • X-rays(eg. radiological and engineering applications) • gamma rays(eg. medical treatment) WHAT IS ELECTROMAGNETIC SPECTRUM? Click here for introduction video to electromagnetic spectrum 13.1 PROPERTIES OF ELECTROMAGNETIC SPECTRUM What is the Electromagnetic Spectrum? • The electromagnetic spectrum consists of electromagnetic waves of a continuous range of wavelength/frequency. 13.1 PROPERTIES OF ELECTROMAGNETIC SPECTRUM 13.1 PROPERTIES OF ELECTROMAGNETIC SPECTRUM What type of Waves are Electromagnetic Waves? • Electromagnetic waves are transverse waves. • The electric and magnetic fields are oscillating perpendicular to each other and to the direction of propagation of the wave. 13.1 PROPERTIES OF ELECTROMAGNETIC SPECTRUM How do Electromagnetic waves propagate? • Electromagnetic waves transfer energy from one place to another without the need for a physical medium. • Electromagnetic waves travel at a speed of 3.00 x 108 m/s in vacuum. • All electromagnetic waves obey the laws of reflection and refraction. 13.1 PROPERTIES OF ELECTROMAGNETIC SPECTRUM How do Electromagnetic waves propagate? • The speed v of electromagnetic waves is related to the wavelength and frequency by the following wave equation: 𝑣 = 𝑓𝜆 • The frequency of an electromagnetic wave depends only on its source. The wavelength and speed of an electromagnetic wave depends on the refractive index of the medium in which it is travelling. • All electromagnetic waves except for visible light are invisible to the human eye. 13.2 COMPONENTS OF ELECTROMAGNETIC SPECTRUM 13.2 COMPONENTS OF ELECTROMAGNETIC SPECTRUM • The electromagnetic spectrum is a continuous range of waves with extremely short wavelengths and high frequencies at one end and extremely long wavelengths and low frequencies at the other end. • The components of the electromagnetic spectrum are classified according to increasing wavelengths or frequencies. The frequencies determine the amount of energy and behaviour of the type of radiation. 13.2 COMPONENTS OF ELECTROMAGNETIC SPECTRUM Electromagnetic Spectrum Gamma rays X-rays Ultra-violet waves Visible light Infra-red radiation Microwaves Radio waves 13.2 COMPONENTS OF ELECTROMAGNETIC SPECTRUM How do you remember the order of the components of the electromagnetic spectrum? How about a singing a song to remember the order? (Click Here!) 13.2 COMPONENTS OF ELECTROMAGNETIC SPECTRUM How do you remember the order of the components of the electromagnetic spectrum? Using Mnemonic 13.2 COMPONENTS OF ELECTROMAGNETIC SPECTRUM Using Mnemonic Example: Raging Martians Invaded Venus Using X-ray Guns EXAMPLE 1 Gamma rays P Ultra-violet Visible rays light Q Radio waves The diagram represents the range of radiations in the electromagnetic spectrum. Name the two radiations labelled P and Q. P : X-ray Q : Infra-red rays or Microwaves EXAMPLE 1 Gamma rays P Ultra-violet Visible rays light Q Radio waves The diagram represents the range of radiations in the electromagnetic spectrum. Complete the following: Compared to radio waves, gamma radiation has __________________ frequency; __________________ wavelength; __________________ speed in vacuum. 13.3 APPLICATIONS & USES OF ELECTROMAGNETIC SPECTRUM Radio Waves Description Lowest frequencies and longest wavelengths. Used for transmission of signals and data. An antenna is used to receive these signals. Uses Radio broadcasting Telecommunication Wireless networking Television transmission 13.3 APPLICATIONS & USES OF ELECTROMAGNETIC SPECTRUM Microwaves Description Uses Easy to control and direct Satellite In a microwave oven, communication/ broadcast absorbed microwaves cause water molecules in the food For cooking food to vibrate rapidly, which then Remote sensing heats up the food. (radar) 13.3 APPLICATIONS & USES OF ELECTROMAGNETIC SPECTRUM Infrared waves Description Produced by hot objects. Some animals can see in infrared red light to enable them to detect warmblooded animals. Uses Night vision binoculars Thermal imaging Remote controls Motion detectors (in security systems) 13.3 APPLICATIONS & USES OF ELECTROMAGNETIC SPECTRUM Visible Light Description Uses Produced by luminous objects Optical fibres for data transmission (e.g. burning items and stars such as the Sun). Endoscopy (visual Crucial for normal human sight. inspection of internal organs) Used in data transfer in Photography telecommunications and by electronic devices such as television sets and computer monitors. 13.3 APPLICATIONS & USES OF ELECTROMAGNETIC SPECTRUM Ultraviolet rays Description Uses The human skin produces vitamin D Sunbeds (tanning machines for indoor tanning) naturally when exposed to ultraviolet rays. In ‘black lights’ for medicine, Also causes tanning by stimulating the forensics, lighting effects, production of the skin pigment known as polymerization and insect melamine. Can cause sunburn. attraction Some chemicals absorb ultraviolet Fluorescence effect. radiation and then appear to be Fluorescent objects like glowing. This fluorescence effect is diamonds absorb UV rays and convert it to visible light used to create markings on bank notes, paints and dyes. 13.3 APPLICATIONS & USES OF ELECTROMAGNETIC SPECTRUM X-ray Description Uses High frequencies. In scanners in airports Able to penetrate many to check the contents of materials. luggage bags Used in the medical field Detecting cracks in pipes and buildings to obtain images of the internal parts of our Radiography bodies. (diagnostic X-ray images in medicine) 13.3 APPLICATIONS & USES OF ELECTROMAGNETIC SPECTRUM Gamma Rays Description Waves with the highest frequency and most energy. Dangerous rays coming from nuclear explosions and atomic bombs which can cause cell and tissue injury. As they can cause damage to living cells, they are used in the medical field to kill cancer cells. Uses Sterilisation of medical equipment Radiotherapy