waves and em spectrum

• waves transfer energy and information without transferring matter
• When a wave travels, energy is transferred but the matter itself does not move. Particles of water or air vibrate and transfer energy but do not move with the wave. This can be shown by placing a cork in a tank of water and generating ripples across the surface - the cork shall bob up and down
• frequency is the number of waves passing a point per second, measured in hertz (Hz)
• wavelength is the distance from one wave crest to the next wave crest, or one wave trough to the next wave trough
• amplitude is the maximum displacement of a wave from its undisturbed position, measured in metres
• the period of a wave is the time taken for one complete wave to pass a point
• the wave front is the line of energy that travels out from the source of the wave
• In transverse waves, particles vibrate perpendicular to the wave direction - e.g. visible light, UV, gamma etc
• In longitudinal waves, particles vibrate parallel to wave direction, through a series of compressions and rarefactions - e.g. sound waves, seismic waves
• Waves change speed when they pass across the boundary between two different substances, such as light waves refracting when they pass from air to glass. This causes them to change direction and this effect is called refraction.
• FAST (Faster Away Slower Towards) - in terms of refraction and the normal
• different substances may absorb, transmit, refract or reflect waves in ways that vary with wavelength
• Reflection is when a wave changes direction, at which the angle of incidence is equal to the angle of reflection
• all electromagnetic waves are transverse, that they travel at the same speed in a vacuum
• RMIVUXG (Rich Men In Vegas Use X-ray Glasses) - Radio waves Microwaves Infrared Visible light UV X-ray Gamma
• ROYGBIV (Red Orange Yellow Green Blue Indigo Violet)
• the electromagnetic spectrum is continuous from radio waves to gamma rays and the radiations within it can be grouped in order of decreasing wavelength and increasing frequency
• our eyes can only detect a limited range of frequencies of electromagnetic radiation
• different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with wavelength
• the potential danger associated with an electromagnetic wave increases with increasing frequency
• Radio waves can be used for broadcasting and general communication - they do not pose any dangers
• Microwaves can be used for cooking, communication and satellites. However, they can cause internal heating of body cells.
• Infrared radiation can be used for cooking, TV remotes and thermal sensors - however, it can cause skin burns.
• visible light is used for general vision, light and photography - it has no dangers
• UV radiation is used in sunbeds, security markings and sterilizing of equipment. However, it can cause skin cancer
• X-rays are used in observing internal structures, and airport security. However, they can cause mutation and cell damage
• Gamma rays can be used to kill cancer cells, detect them and sterilize equipment - however, they can cause mutation and cell damage.
• radio waves can be produced by, or can themselves induce, oscillations in electrical circuits
• changes in atoms and nuclei can generate radiations over a wide frequency range, and be caused by absorption of a range of radiations