Section 3- Waves Flashcards
What is the use of hertz
- used for frequency
- the number of cycles per second of something which repeats regularly
What are transverse and longitudinal waves?
- in a transverse wave, the displacements (certain points on the wave moving) /oscillations/ vibrations are perpendicular ( at right angles) to the direction of energy transfer (e.g light waves and waves seen in water)- these waves can be demonstrated on springs (springs can also demonstrate longitudinal)
- in longitudinal waves, the displacements/oscillations/vibrations are parallel (in the same direction) as the direction of energy transfer. E.g sound waves are longitudinal
BOTH TRANSFER ENERGY
What is the period of a wave?
(Time) period for one wave to pass a point- different to frequency which is how many waves pass a point in an amount of time
MEASURED IN SECONDS
How is the (time) period of a wave calculated?
What is the frequency of a wave?
-The number of waves that pass a point in one second e.g. if two waves pass a point in one second the frequency would be 2Hz
MEASURED IN HERTZ (Hz)
What is the amplitude of a wave?
The maximum disturbance of a wave from the equilibrium
What is the equilibrium of a wave?
The horizontal midpoint of a wave
What is wavelength?
The distance between a particular point on one wave and the same point on the next wave
What is the compression of a wave?
The more dense part of a longitudinal wave
What is the rarefraction of a wave?
The less dense part of a longitudinal wave
What is the crest on a wave?
The highest point on a transverse wave form
What is the trough on a wave?
The lowest point on a transverse waveform
How does energy travel?
- without particles or transfer of matter
- some waves travel without the use of particles at all, e.g light (electromagnetic) waves
- others cause particles to vibrate, but eventually return to their original position
- we call the material that a wave passes through a ‘medium’
How do we calculate the wave speed of a wave?
Speed=frequency x wavelength
v=f x (lambda sign)
what is m/s ^-1 the same as?
What is the Doppler effect?
- the idea that a moving object emitting waves had bunched waves with a higher frequency in front of it, and mor spread out waves behind it with a lower frequency
- e.g as an ambulance moves towards you, the pitch is higher, then as it moves past and away from you, the pitch becomes lower
What is redshift?
- red shift is the same idea as the Doppler effect, but with light. From our perspective, Galaxies moving towards us have compressed wavelengths and therefore their wavelengths are shifted to the blue end of the spectrum. If it is moving away from us then the wavelengths are shifted to the red end of the spectrum
- The amount of redshift is dependant on the speed at which the galaxy is moving to/away from us
- on the whole, we can see that most galaxies are moving away from us, proving that the universe is expanding
- we can also see that universes further away from us are moving faster
How are waves reflected?
- all waves can be reflected.
- if they hit a straight/flat barrier, the angle at which they leave the barrier surface is equal to the angle at which they ,set the surface
- the reflected wave is also the same distance from the normal as the original wave
- the angle of incidence is the angle of the original wave from the normal
- the angle of reflection is the angle of the reflected wave from the normal
- the direction of the reflected wave is away from the barrier
How are waves refracted?
- if a ray moves from a less dense medium to a more dense medium, the ray will be refracted towards the normal
- if a ray travels from a more dense medium to a less dense medium, it will be refracted away from the normal
- if the ray enters the glass block at 90 degrees (ie along the normal) so it has an angle of 0 degrees from the normal, it will not refract and it will pass straight through
What are the components of the electromagnetic spectrum? In order
Radio, microwave, infrared, visible light, ultra violet, x-rays, gamma
Which wave in the electromagnetic spectrum has the lowest/highest wavelength/frequency
Wavelength: radio waves have the longest, gamma rays have the shortest
Frequency: radio waves have the lowest, gamma rays have the highest
What is the speed of the electromagnetic waves in free space (vacuum)
they are the same
What colours is white light made up of?
All the colours of the visible spectrum
Which colour light has the longest wavelength?
Which colour light has the shortest wavelength?