1.5 Waves Flashcards
What are two types that a wave can be categorised by?
Transverse
Longitudinal
Describe the properties of a transverse wave
The direction of oscillation is perpendicular to the propagation of the energy of the wave
What shape is a transverse wave?
S on it’s side
Describe the properties of a longitudinal wave
The direction of oscillation is parallel to the propagation of energy of the wave
What shape is a longitudinal wave?
Looks like a spring
What is the frequency of a wave?
How many waves per second
In longitudinal waves what is rarefaction?
When the waves are spaced out
In longitudinal waves what is compression?
Where the waves are close together
Give an example of transverse waves
The electromagnetic waves
Give an example of longitudinal waves
Sound waves
What waves can be transverse or longitudinal?
Mechanical waves
What do waves do?
Transfer energy
What waves are in the electromagnetic spectrum from low frequency to high frequency?
Radio-waves Microwaves Infrared radiation Visible light Ultra violet X-rays Gamma rays
What properties does the left side of the spectrum have (Radio-waves)
Low frequency
Long wave length
Low energy
Least penetrating
What properties does the right side of the spectrum have (Gamma rays)
High frequency
Short wave length
High energy
Most penetrating
What is wave speed?
300,000,000 m/s
Give an example of a use for radiowaves
TV
Give an example of a use for microwaves
Mobile phone
Give an example of a use for infrared radiation
Heater
Give an example of a use for ultraviolet
Identifying money
Give an example of a use for x-rays
Finding broken bones
What is frequency measured in?
Hertz (Hz)
What is refraction?
The direction when sound or light waves pass across a boundary of two substances
Why do the waves change direction in refraction?
The two substances will have different densities causing the speed to change
What acronym help remember the changes in the waves when refracted?
TAGAGA Towards (the normal) Air to glass Away (from the normal) Glass to air
If the wave is travelling along the normal in refraction what happens?
The wave will not change direction
How do different waves lengths affect refraction? Specifically visible light?
They are refracted differently
Violet - refracted the most
Red - refracted the least
What is diffraction?
The spreading of waves through a gap or round an obstacle
What does the extent of the spreading of the wave in diffraction depend on?
The width of the gap compared with the wavelength
What happens if a gap is similar to the wavelength in diffraction?
The wavelength is spread a lot (big waves out the other side)
What happens is the gap is a lot bigger than the wavelength in diffraction?
The wavelength is spread very little
Small waves out the other side
How can people in hilly areas be affected in terms of diffraction?
Signals may be blocked by a hill because they may not diffract enough around a hill
What is the normal in reflection?
An imaginary line perpendicular to a mirror
What is the angle of incidence?
The angle between the incoming ray and the normal
What is the angle of reflection?
The angle between the reflected ray and the normal
What is the link between the angle of incidence and the angle of reflection?
They are the same size
How do smooth surfaces affect reflection?
Strong echoes for sound
Strong line of light in mirrors
How do rough surfaces affect reflection?
Scatter sound and light in all directions
But they still follow the angle rules
What is sound?
Vibrations in a medium detected as sound
What can sound travel through?
Solid
Liquid
Gas
Not a vacuum
What is pitch of sound determined by?
Frequency and amplitude
What are reflections of sound?
Echoes
What is the big bang theory?
A small singularity where everything was densely packed
For an unknown reason it exploded and released elements and matter
Around 13.7 billion years ago
What is the doppler effect?
The perceived change in wave length due to the motion and the observer
When the sources moves towards the observer what happens in the doppler effect?
Frequency increases
Wavelength decreases
When the source moves away from the observer what happens in the doppler effect?
Frequency decreases
Wavelength increase
Name pieces of evidence that supports the big bang
Red shift
Cosmic microwave background radiation
What is red shift?
A perceived change in wavelength as the waves are stretched or getting longer moving into the red end of the spectrum
Why is red shift evidence for the big bang?
There is an observed increase in wavelength of light from most distant galaxies
So galaxies are still expanding further away so they must have originally been squashed together
What is Hubbles law?
The further away the galaxy the faster they are moving
Therefore the bigger observed increase in wavelength
What is the cosmic microwave background radiation?
The beginning of the universe was very hot so electromagnetic radiation filled the universe
The radiation that was present is visible as an echo of light radiation from the big bang
Who’s and what theory opposes the big bang?
Sir Fred Hoyle
The steady state theory
What is the steady state theory?
The universe has no start and is alway expanding
What is evidence for the steady state theory?
Red shift
