Electromagnetic waves

• Radio waves are used for TV and radio signals.
• Microwaves are used for satellite and mobile phone communications, and cooking food.
• Infrared radiation is used in remote controls, night vision goggles, and heat-sensing cameras.
• Visible light is used for fibre optic communications. It has a short wavelength. Hazard: too bright a light can damage the eyes.
• Ultraviolet radiation is used for sterilisation of water and food, artificial sun tanning. Hazard: UV can damage skin cells and cause premature aging.
• X-rays: used for medical imaging. Pass easily through flesh but not through denser materials like bone.
• Gamma rays: very short wavelength.
• electromagnetic waves are transverse waves
• Why are electromagnetic waves not mechanical waves?

  They can travel through a vacuum (don't need a substance to travel through)
• List the different types of wave in the electromagnetic spectrum in order of decreasing wavelength?

  radio, microwave, infrared, visible, ultraviolet, x-ray, gamma
• which part of the EM spectrum can humans see?

  visible light
• how are gamma waves be produced?

  changes in the nucleus of an atom, for example during radioactive decay
• how can radio waves be produced?

  oscillations in an electric circuit
• how can we detect radio waves?

  wave are absorbed and create an alternating current with the same frequency as the radio wave
• what are radio waves used for?

  transmitting television, mobile phone, Bluetooth signals
• what are microwaves used for?

  satellite communications, cooking food
• why are x-rays used for medical imaging?

  they can pass through flesh but not bone
• why are gamma rays used for treating cancer and sterilising medical equipment?

  high does kill cancer cells and bacteria
• What is refraction?

  waves change speed and direction as they cross the boundary from one sustance to another
• Radio waves have a wavelength of 1m - 10 000m
• Radio waves can travel long distances and can be reflected off the surface of the earth.
• Longer radio wave wavelengths can bend around obstructions to allow detection of signals when not in line of sight.
• Gamma rays pass easily through the body. Used for cancer treatment to kill cancerous cells.
• X-rays hazard: form of ionising radiation, can damage cells and cause cancer.
• Microwaves have a wavelength of about 1cm.
• Microwaves can pass through the Earth's atmosphere to reach satellites.
• Microwaves can penetrate into food and are absorbed by water molecules inside food which vibrate and then heat the food.
• Microwaves Hazard: they can penetrate the body and cause internal heating.
• All hot objects emit infrared waves, sensors use these to create an image.
• Infrared waves can transfer energy quickly to heat rooms.
• Infrared Hazard: can damage or kill skin cells due to heating.