waves part 1 basics what is a wave? a wave is a disturbance that carries energy through matter or...
TRANSCRIPT
WavesPart 1
Basics
What is a wave?
•A wave is a disturbance that carries energy through matter or space
Waves Themes
These are some of the areas of interest that involve waves
1. Sight and vision2. Sound and hearing3. Communications4. Medicine5. Cooking6. astronomyAnd more…………
The uses of waves
1. Microwave
2. Radar
3. Mobile
4. TV
5. Radio
6. CD
7. Music
8. Satellite
1. X-rays
2. Ultrasound
3. Gamma-rays
4. Fibre optics
5. Remote control
6. …..
7. …..
Waves
The characteristics of waves
Waves are
1. Regular patterns of disturbance
2. Made by vibrations
They
3. Transmit energy
4. Do not transmit matter
Waves
The two main types
Transverse (b)1. on a rope 2. on the surface of
water3. light
Longitudinal (a)
1. in a spring
2. Sound
longitudinal
transverse
• When a crowd does “the Mexican wave” at a sporting event, they are performing as a transverse wave
• The wave moves in a circle around the stadium, but the people move up and down
Transverse WavesWaves
Transverse particle motion
Waves
Transverse particle motion
The motion of the particles in the medium is at a right angle to the motion of the
wave as a whole
Waves
Transverse particle motion
Waves
Longitudinal
The particles move in the same direction as the wave motion
Waves
Terms – wavelength - longitudinal
Compression (C) – rarefaction (R)
λC R C R C R
=wavelength
Waves
Terms – wavelength - transverse
Crest (C) –Trough (T)
T T
C C Cλ =wavelength
Waves
Terms – wavelength
Wavelength The distance between two consecutive
• Crests or troughs• Compressions or rarefactions
Waves
Terms – amplitude - longitudinal
Amplitude
The maximum (biggest) disturbance or displacement.
Waves
Terms - frequency
Frequency
The number of waves made or passing by in 1 second
Unit – Hertz (Hz)
Waves
Terms - speed
Speed
The distance a wave travels in one second.
start 1 second later
Waves
Symbols and units
unit symbol
amplitude m A
wavelength m λ or w
frequency Hz f
speed m/s s,v or c!
Waves
Formula
s,v or c -speed
w or λ – wavelength
s
f λ
Waves on water
Waves
Transverse waves on water – a side view
Direction of travel
Particle motion – not 100% correct!
Waves
Transverse waves on water – from above
= wave motion
= crest
= source
Waves travelling out from the source
Waves spreading
The previous slides show waves moving
along a line.
Waves can spread out moving
• across the surface of the sea ( 2 dimensions)
• or through space ( 3 dimensions)
Waves
Light and sound
Light
1. Transmits energy
2. Transverse
3. Does not need a medium – can travel through empty space
Sound
1. Transmits energy
2. Longitudinal
3. Needs a medium – solid – liquid - gas
Wave Interactions--Reflection
•Reflection is what happens when a wave strikes a surface or boundary
• Waves reflect at a free boundary
• At a fixed boundary, waves reflect and turn upside down
Waves
Reflection -sound
1. Sound is reflected when it meets a boundary between two materials – air/brick.
2. Reflected sound can produce an echo.
Echo - reflection
Waves
Reflection – spring waves
Waves can be reflected at the fixed end of a spring.
Waves
Reflection - light
1. Light is reflected when it meets a boundary between two materials – air/mirror – air/paper.
2. Light reflected by a mirror produces an image.
Waves
Reflection – light - diagrams
Reflection by a plane mirror
Waves
Reflection – water waves - diagrams
Water waves are reflected by barriers
Waves
Refraction - light
• When waves pass from one medium into another, they are bending due to a process called refraction
• This is why a spoon looks like it is broken into 2 pieces when it is resting in a glass half-full of water
Waves
Refraction – light - diagrams
There is some reflection as well.
Waves
Refraction- water waves – diagrams -1
When water waves pass from deep water to shallow water they slow down. The wavelength decreases .
deep-fast shallow-slow
Waves
Refraction- water waves – diagrams -2
deep shallow
The direction changes as well – this is refraction
Waves
Diffraction
Waves spread when they
1. pass through a gap
2. go past an obstacle
Waves
Diffraction – narrow slit
Narrow slit – more diffraction
Waves
Diffraction – wide slit
Wide slit – less diffraction
Waves
Diffraction – past an obstacle -1
Short radio waves – less diffraction
Radio
transmitter
No reception
Waves
Diffraction – past an obstacle -2
Long radio waves – more diffraction
Radio
transmitter
reception