EM waves

• What are Electromagnetic waves?

  Transverse waves
• All Electromagnetic waves travel at the same velocity (the speed of light) in air or a vacuum
• The electromagnetic spectrum extends from low frequency , low energy waves to high frequency , high energy waves
• Humans are only capable of detecting visible light (A very limited range of EM waves)
• The wavelength of an electromagnetic wave affects how it is absorbed , transmitted , reflected and refracted . This affects how the EM wave is used
• What are the uses for radio waves?

  Televisions , Radio and bluetooth
• Why are radio waves used for radio transmission?

  Radio waves are low energy waves , making them not harmful and ideal for radio transmission
• What are microwaves used for?

  Satellite communication and cooking food
• Why are microwaves used in satellites?

  They travel in straight lines through the atmosphere which makes them ideal for transmitting signals to satellites and back down to recievers
• What are Infrared waves used for?

  Electrical heaters , cooking food and infrared cameras
• Why are infrared waves used in electrical heaters and grills / toasters?

  They glow red hot as electricity flows through them, which transmits infrared energy that is absorbed by the food and converted back into heat
• What is visible light used in?

  Fibre optic communications
• Why is visible light used in fibre optic communications?

  Visible light travels down optical fibres from one end to the other without being lost through the sides
• What are Ultraviolet waves used for?

  Energy efficient light bulbs , security marking and sunbeds
• Why are UV waves used in energy efficient light bulbs?

  In these light bulbs, UV waves are produced by the gas in the bulb when it is excited by the electric current . These waves are absorbed by the coating on the bulb which fluoresces giving off visible light
• What are X-rays used for?

  Medical imaging and treatments
• Why are X rays used in medical imaging?

  X rays can penetrate soft tissue but not bone . A photographic plate behind a person will show where bones are
• What are gamma rays used for?

  Sterilising food and treatment of tumours
• Why are gamma rays used in treatment of tumours?

  They are the most energetic of all EM waves can be used to destroy bacteria and tumours
• What results in EM waves being generated or absorbed over a wide frequency range?

  Changes in atoms and the nuclei of atoms
• Electrons moving between energy levels ,as a result of heat or electrical excitation can generate waves (e.g. x-rays)
• Changes in the nucleus of an atom can generate waves
• Ultraviolet waves , X - rays and gamma rays carry enough energy to have a hazardous effect on the human body
• What makes gamma rays hazardous?

  They can cause the skin to age prematurely and increase the risk of skin cancer
• What makes X-rays can gamma rays dangerous?

  They are ionising radiation - they can damage cells by ionising atoms and if absorbed by the cells nucleus , they can cause gene mutations and cancer