2.6 - Electromagnetic Waves

What kind of waves are electromagnetic waves?

transverse waves

What do all electromagnetic waves do?

• transfer energy as radiation from the source of the waves to an absorber

• can travel through a vacuum such as in space

• travel at the same speed through a vacuum or the air

How fast do all electromagnetic waves travel?

300 million metres per second (m/s) through a vacuum, the speed of light

What do electromagnetic waves form?

a continuous spectrum of waves

What are the distinctions between the continuous spectrum of waves?

• waves with a very short wavelength, high frequency and high energy

• waves with a very long wavelength, low frequency and low energy

What part of the electromagnetic spectrum is 1?

radio waves

What part of the electromagnetic spectrum is 2?

microwaves

What part of the electromagnetic spectrum is 3?

infrared radiation

What part of the electromagnetic spectrum is 4?

visible light

What part of the electromagnetic spectrum is 5?

ultraviolet

What part of the electromagnetic spectrum is 6?

x-rays

What part of the electromagnetic spectrum is 7?

gamma rays

What part of the electromagnetic spectrum is 8?

• long wavelength

• low frequency

• low energy

What part of the electromagnetic spectrum is 9?

• short wavelength

• high frequency

• high energy

What does the behavior of an electromagnetic wave in a substance depend on?

frequency

What are long wavelength electromagnetic waves?

• radio waves

• microwaves

• infrared

• visible light

What are short wavelength electromagnetic waves?

• ultraviolet

• x-ray

• gamma ray

What is the frequency range of radio waves?

10⁵ - 10¹⁰ Hz

What is the wavelength range of radio waves?

10³ - 10^-2 m

What is the frequency range of microwaves?

10¹⁰ - 10¹¹Hz

What is the wavelength range of microwaves?

10^-2 - 10^-3m

What is the frequency range of infrared radiation?

10¹¹ – 10¹⁴Hz

What is the wavelength range of infrared radiation?

10^-3 - 10^-6 m

What is the frequency range of visible light?

10¹⁴ - 10¹⁵Hz

What is the wavelength range of visible light?

10⁶ - 10^-7m

What is the frequency range of ultraviolet?

10¹⁵ - 10¹⁶Hz

What is the wavelength range of ultraviolet?

10^-7 - 10^-8

What is the frequency range of x-rays?

10¹⁶ - 10¹⁸Hz

What is the wavelength range of x-rays?

10^-8 - 10^-10m

What is the frequency range of gamma rays?

10¹⁸ - 10²¹Hz

What is the wavelength range of gamma rays?

10^-10 - 10^-14m

How are radio waves produced?

oscillations in an electrical circuit

What are radio waves absorbed by?

by a receiver aerial

What happens when radio waves are absorbed?

they may create an alternating current with the same frequency as the radio waves

What can EM waves of a wide range of frequencies do?

be absorbed or produced by changes inside an atom or nucleus

How are gamma rays produced?

changes in the nucleus of an atom

What happens when electrons in an atom move down energy levels?

they emit EM waves

What are the uses of radio waves?

television and radio signals

Why are radio waves suitable for their use?

• can travel long distances through air

• longer wavelengths can bend around obstructions to allow detection of signals when not in line of sight

What are the hazards of radio waves?

can penetrate the body and cause internal heating

What are the uses of microwaves?

• satellite communicates

• cooking food

Why are microwaves suitable for their use?

• can pass through Earth’s atmosphere to reach satellites

• can penetrate into food and are absorbed by water molecules in food heating it

What are the hazards of microwaves?

can penetrate the body and cause intern at heating

What are the uses of infrared?

• electrical heaters

• cooking food

• infrared cameras

Why is infrared suitable for their use?

• all hot objects emit infrared waves sensors can defect these to turn them into an image

• can transfer energy quickly to heat rooms and food

What are the hazards of infrared?

can damage or kill skin cells due to heating

What are the uses of visible light?

fibre optic vommunications

Why is visible light suitable for their use?

short wavelength means visible light carries more information

What are the hazards of visible light?

can damage the retina

What are the uses of ultraviolet?

energy efficient lights and artificial sun tanning

Why is ultraviolet suitable for its use?

• carries more energy than visible light

• some chemicals used inside light bulbs can absorb UV and emit visible light

What are the hazards of ultraviolet?

can damage skin cells causing skin to age prematurely and increasing the risk of skin cancer and can cause blindness

What are the uses of x-rays?

medical imaging and treatments

Why is x-rays suitable for their use?

• pass easily through flesh but not denser materials like bone

• high doses kill living cells, so can be used to kill cancer cells

What are the hazards of x-rays?

form of ionising radiation which can kill or damage cells, cause mutation of genes and lead to cancers

What are the uses of gamma rays?

medical imaging and treatments

Why is gamma rays suitable for its use?

• pass easily through flesh but not denser materials like bone

• high doses kill living cells, so can be used to kill cancer cells - gamma rays can also be used to kill harmful bacteria

What are the hazards of gamma rays?

form of ionising radiation which can kill or damage cells, cause mutation of genes and lead to cancers