Waves Flashcards
What do waves do?
Transfer energy in the direction they are travelling
When waves travel through a medium the particles of the medium oscillate and transfer energy between each other but the particles stay in the same place. Only energy is transfered
Waves have 3 things. What are they?
Amplitude- maximum displacement of a point on a wave from its undisturbed position
Wavelength- distance between the same point on two adjacent waves
Frequency- number of waves passing a certain point per second
(See annotated diagram on page 105 of revision guide for more)
What is the formula for frequency of a wave?
Period (T) = 1/ frequency (f)
Frequency measured in hertz Hz
Period measured in seconds s
What kinds of vibrations do transverse waves have?
Transverse waves have perpendicular vibrations to the direction of energy transfer.
What waves are transverse?
All waves on the electromagnetic spectrum
Ripples and waves in water
A wave on a string
What kind of vibrations do longitudinal waves have?
Oscillations are parallel to the direction of energy transferred
What are examples of longitudinal waves?
Sound waves in air, ultra sound
Shockwaves eg some seismic waves
What is the wave speed equation?
Wave speed (m/s) = frequency (Hz) x wavelength (m)
v=f x (that landa sign thingy)
What is wave speed?
The speed at which energy is being transferred.
How to use an oscilloscope to measure the speed of sound and speed of water ripples?
See page 107 of revision guide
Don’t think we have covered this
How to find wave speed of wave on a spring?
Set up signal generator, vibration transducer, string, pulley and mass (as shown on of 108 of revision guide).
Turn on signal generator and vibration transducer. The string will start to vibrate
You can adjust frequency to change wave length . Adjust until there’s a clear wave (happens when whole number of half waves fit on a string), depends on length of string and masses
Measure wavelength using ruler
Frequency of wave is whatever signal generator is set too
Use wave length equation to find wave speed
(For more clarity see 108 in revision guide)
What is refraction?
When light waves are bent when they enter a new media
When wave arrives at a boundary between 2 different materials, what are the 3 things that can happen?
Wave is ABSORBED by second material- transfers energy to materials energy store. This often leads to heating. Can be used in microwaves
Wave is TRANSMITTED through the second material- waves carry on travelling through the new material. This often leads the refraction. Used in glasses lenses and cameras and communication
Wave is REFLECTED- it’s sent back away from second material
Which of these happens depends on wavelength and properties of materials
Explain refraction
When a wave crosses a boundary between 2 materials it changes speed
If a wave is travelling along the normal it will change speed but not refracted, If hit at an angle is changes direction and is refracted
Waves bends towards normal if it slows down and away from it if it speeds up- how much it’s refracted depends on change in speed which depends on density of material, higher density slower wave
When a wave is refracted what changes and what stays the same?
Wave length changes but frequency stays the same
What is optical density?
A measure of how quickly light can travel through it, higher optical density, slower light travels through it
How do you construct a ray diagram to show refraction?
Draw boundary between two materials
Draw normal line perpendicular to boundary
Draw incident ray that meets normal at the boundary. Angle between ray and normal is angle of incidence
Draw refracted ray in other side. Angles between refracted ray and normal is small than angle of incidence unless second material is less optically dense.
What type of waves are those on the electromagnetic spectrum?
Transverse waves that’s transfer energy from a source to an absorber
What speed do different EM waves travel at?
All Em waves travel at the same speed through air or a vacuum
Finish the blanks. Electromagnetic waves form a _________ over a range of ___________. They are grouped into 7 basic types based on their ______ and _________
Continuous spectrum
Frequencies
Wave length
Frequency
What are the 7 wave types on the EM spectrum?
Radio waves Micro waves Infra red radiation Visible light Ultra violet X rays Gamma rays