Transcript
WAVES
9.2 Waves• A wave is an oscillation that travels from one
place to another.• If you poke a floating ball, it oscillates up and
down.• The oscillation spreads outward from where it
started making a wave
9.2 Waves• A disturbance has to create a wave. When you drop a
ball into water, some of the water is pushed aside and raised by the ball. The ball doesn’t travel with the wave, the energy of the wave just passes through!
9.2 Waves
• Waves are a traveling form of energy because they can change motion.
• Waves also carry information, such as sound, pictures, or even numbers.
Did you know?
• All of the information that you receive in your __________ and _________ comes from waves!!!
9.2 Frequency, amplitude, and wavelength
• You can think of a wave as a moving series of high points and low points.
• A crest is the high point of the wave.• A trough is the low point of a wave.
9.2 Frequency, amplitude, and wavelength
• Wavelength is the distance from any point on a wave to the same point on the next cycle of the wave.
• The distance between one crest and the next crest is a wavelength.
9.2 Frequency, amplitude, and wavelength
• The amplitude is the maximum amount the wave moves away from equilibrium.
• Equilibrium is the average or resting position
PARTS OF A WAVE
equilibriumamplitude
Which type of wave is the fastest, water, light or sound?
• Water: couple of miles per hour
• Light: 670,616,629 miles per hour (186,282 miles/second!!!)
• Sound: 660 miles per hour
9.2 Transverse waves
• The oscillations of a transverse wave are not in the direction the wave moves.
9.2 Longitudinal waves
• Longitudinal waves do oscillate in the same direction that the wave travels (Spring hooked to the wall)
9.2 The speed of waves• The speed of a water wave is how fast the
wave spreads, NOT how fast the water surface moves up and down or how fast the dropped ball moves in the water.
How do we measure the wave speed?
9.2 The speed of waves
• A wave moves one wavelength in each cycle.
• Since a cycle takes one period, the speed of the wave is the wavelength divided by the period.
9.2 The speed of waves
• The speed is the distance traveled (one wavelength) divided by the time it takes (one period).
• We usually calculate the speed of a wave by multiplying wavelength by frequency.
Formulas for Wave Speed
• Speed = frequency x wavelength
• Speed = wavelength / period
**Wavelength is measured in meters, frequency is measured in hertz, period is measured in seconds, speed is measured in m/s.
9.2 When a wave encounters objects
• When a wave hits an object or a surface called a boundary, four things can happen.
9.2 Reflection• When a wave bounces off an object we call it
reflection. • A reflected wave is like the original wave but
moving in a new direction.
9.2 Refraction• Refraction occurs when a wave bends as it
crosses a boundary.• We say the wave is refracted as it passes
through the boundary.
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