# Waves

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• WAVES
• The nature of waves
• We use waves to transfer energy and transfer infomation
• Transverse waves vibrate at right angles to the direction of energy transfer of the waves. all electromagnetic waves are transverse waves
• Longitudinal waves vibrate parallel to the direction of energy of the waves. a sound wave is an example of a longitudinal wave
• Mechanical waves, which need a medium to travel through, maybe transverse or longitudinal waves
• Measuring waves
• For any waves, its amplitude is the height of the waves crest or the depth of the waves trough from the position at rest
• For any wave, its frequency is the number of wave crest passing a point in one second
• For any waves, its wavelength is the distance from one wave crest to the next wave crest. this is the same as the distance from one wave trough to the next wave trough
• Reflection
• The normal at a point on a mirror is a line drawn perpendicular to the mirror
• the angle of of incidence is the angle between the incident ray and the normal
• the angle of reflection is the angle between the reflected ray and the normal
• The angle of incidence = the angle of reflection
• Refraction
• Refraction is the change of direction of waves when they travel across a boundary
• When a light ray refracts as it travels from air into glass, the angle of refraction is less than the angle of incidence
• When a light ray refracts as it travels from glass into air, the angle of refraction is more than the angle of incidence
• Diffraction
• Diffraction is the spreading out of waves when they pass through a gap or round the edge of an obstacle
• The narrower a gapis, the greater the diffraction is