W AVES. W AVES AND E NERGY Waves and Energy Wave – a traveling disturbance that carries energy...
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Transcript of W AVES. W AVES AND E NERGY Waves and Energy Wave – a traveling disturbance that carries energy...
WAVES AND ENERGY
Waves and Energy
Wave – a traveling disturbance that carries energy from one place to another
Waves do not carry matter; waves carry energy
Vibration – movement that follows the same path over and over again
Wave – movement of energy from a vibrating source outward
Medium
The matter or substance through which a wave is transmitted
Ex. Water – medium for ocean waves
Air – medium for sound
ELECTROMAGNETIC WAVE
Wave that consists of electric and magnetic fields
Do not require a medium
Ex. Light, microwaves, x-rays
Amplitude
Greatest distance from normal resting position to top (crest) of the wave
Indicates the amount of energy carried by the wave
Wavelength
Distance between two crests or two troughs (lowest point)
Usually measured in meters or centimeters
Symbol for wavelength is lambda λ
Frequency
Frequency – the number of complete waves or complete cycles per unit time
Unit: Hertz (Hz) = 1 wave/second
TRANSVERSE WAVES
A wave in which the motion of the medium is at right angles to the direction of the wave
Movement of particles is up and down – vertical
Movement of the wave is horizontal
Ex Waves on a rope, water waves, light, electromagnetic waves
LONGITUDINAL WAVES
AKA compressional wave
Wave in which the motion of the medium is parallel to the direction of the wave
A series of compressions and rarefactions
Rarefaction – space in the medium in which there are fewer particles
Ex Sound waves
SPEED OF WAVES
Speed = frequency x wavelength Speed of a wave is constant
within the same given medium If frequency is increased then
wavelength must decrease for constant speed to be maintained
The speed of a wave depends upon the medium
The density of the medium affects the speed of mechanical waveso The more dense a medium , the
slower light waves travel but the faster sound waves travel.
Elasticity of the medium affects the speed of waves
Elasticity – ability of a medium to return quickly to its original shape after being disturbed
The more elastic – the faster the wave
LAW OF REFLECTION
The angle of incidence (i) is equal to the angle of reflection (r)
Ray – line drawn in the direction of motion of a wave Incidental ray – incoming ray (incoming
wave)
Reflected ray – ray (wave) that bounces off barrier
Angle of incidence (i) – angle formed by the incident ray and the normal
Angle of reflection (r)- angle formed by the reflected ray and the normal
Normal – line drawn perpendicular to barrier
Refraction
The speed of a wave changes as the wave travels from one medium to another
Refraction – the bending of waves due to a change in speed
Refraction occurs because waves move at different speeds in different mediums
If wave slows down it is bent to the normal
If it speeds up, it is bent away from the normal
INTERFERENCE
Interaction of waves that occur at the same place at the same time; the wave combine to make a single wave
Constructive interference – crest meets crest; the amplitudes add together creating a larger amplitude
Destructive interference – crest meets trough; the amplitudes subtract from one another creating a smaller amplitude
STANDING WAVES
Wave that does not appear to be moving; occurs at the natural frequency of the material
Nodes – points at which destructive interference results in no energy displacement
Antinodes – points at which constructive interference causes maximum energy displacement
Resonance frequency – frequency at which a standing wave occurs
RESONANCE
The ability of an object to vibrate by absorbing energy at its natural frequency
Video
Video 2
POLARIZATION
Alignment of vibrations in a transverse wave
Usually by filtering out waves of other directions
Polarizing filters – transmit only light waves that vibrate in the same plane
Polarized sun glasses Reduce glare