Mocks-waves Flashcards
Wave definition
A wave is produced by a disturbance, vibration,oscillation which transfers energy and information but not matter
wavelength
The distance between any 2 consecutive waves
distance
How far the wave has travelled from its starting point
Displacement
How far from the equilbrium point the wave has oscillated
maximum displacement
amplitude
amplitude
the distance from the rest/median/equilibrium/0 line to the crest or trough.
Amplitude indicates
loudness
Displacement time graph-oscillation is
the time period- the time it takes for one complete oscillation
Frequency =
1/time period
frequency definition
the number of complete waves that pass a point in a second
Time period=
1/frequency
Frequency determines
pitch
Transverse wave
-It is produced when the disturbance/vibration is perpendicular (90 degrees) to the direction of energy transfer (vibrations go up and down whilst the overall wave is going from left to right)
examples of transverSe waves
- electromagneTic waves
- secondary seismic waves (earthquakes)
- ripples/waves
- waves of strings
Longitudinal wave
-It is produced when the disturbance/vibration is parallel to the direction of energy/data transfer (the waves vibrate back and forth so they have compressions and rarefactions).
Examples of longitudinal waves
- primary seismic waves
- sound waves
wavelength
The distance between any 2 consecutive waves
How to measure the wavelength on longitudinal waves
- measure from one compression to the next compression or one rarefaction to the next rarefaction
Period
The time taken for one complete wave to pass a point
Are waves always reflected?
No
When a wave reaches a boundary, it will either
- be absorbed by the material so the energy from the wave is transferrd to that material’s energy stores
- the wave could be transmitted (where the wave enters the material but carries on travelling and passes out other side- often refraction)
- reflection- wave never enters the material
What does the action of a wave depend on?
- wavelength
- properties of two materials
Angle of incidence=
angle of reflection
normal
a dashed line that is perpendicular to the surface
Point of incidence
Where the incoming ray touches the boundary
Mirrors
boundary is flat - all normals are in same direction so all of the incoming light rays will be reflected in the same direction. This is called specular reflection. Gives us a clear image.
Paper
-Relatively rough surface. Boundary different. Normals will be different but incoming light rays the same. Light will be reflected in all different directions. Diffuse/scattered reflection. Normally can’t see ourselves.
Paper
-Relatively rough surface. Boundary different. Normals will be different but incoming light rays the same. Light will be reflected in all different directions. Diffuse/scattered reflection. Normally can’t see ourselves.
sound waves
vibrations that pass through the molecules of a medium
- they are a type of longitudinal wave
- they travel as a series of compressions and rarefactions
compressions
- regions where the vibrating particles are closest together
rarefactions
-regions where the particles are furthest apart
Sound waves travelling through a solid
- sound waves cause particles in the solid to vibrate
- these collide with neighbouring particles, transferring energy and in turn causing them to vibrate
- this occurs throughout the whole solid- sound wave gets transmitted through the material
Sound waves need
particles to travel.
The more densely packed particles are, the
faster the sound travels (sound travels faster in solids than in liquids and gases)
Why can sound not travel through a vacuum?
Because there are no vibrating particles in a vacuum
As sound waves travel between different mediums and speed up and slow down, what does not change?
their frequency does not change
If speed is increasing, (wavespeed = frequency x wavelength)
and the frequency remains the same, the wavelength must increase instead
As sound speeds up, the wavelength
gets longer, which happens in high density mediums like solids.
As the sound slows down, the wavelength will get
shorter, which happens in low density materials like air
Sound changes speed from one medium to another so can be
refracted
Sound changes speed from one medium to another so can be
refracted
sound can be
reflected, refracted or absorbed. Hard, flat surfaces reflect the most sound, giving us echoes.
compressions
regions of higher density
rarefactions
regions of lower density
sound waves are
vibrations of air molecules
Compressions and rarefactions cause
changes in pressure, which vary in time with the wave.
Sound is a type of
pressure wave
Hearing range of humans
- 20 Hz to 20000 Hz. Different people will have slightly different hearing ranges. Older- range of hearing will decrease.
Why does your hearing range decrease as you get older?
Wear and tear of cochlea and auditory nerve.
Sound wave pathway through the ear
The sound waves enter the ear canal. The vibrations cause the ear drums to vibrate which leads to the Malleus, Incus and Stapes to vibrate. Makes fluid in the cochlea vibrate. Makes hair cells vibrate and release neurotransmitters. Sends electrical signals to the brain via the auditory nerve.
Ultrasound
- sound waves above the human hearing range of 20000 Hz
When meeting a boundary between two media,ultrasound may be:
- Partially reflected
- Partially transmitted
- Partially absorbed
The percentage that is reflected or transmitted depends on the
- two media at the boundary:
- An air and glass boundary will have different percentages compared to an air and wall boundary
The percentage of the wave reflected is greatest when
the difference in speed of sound between the media is large.
-For example, when sound in air hits a brick boundary, most of the sound is reflected because waves travel much faster in brick than in air
Echo sounding
Echo sounding uses ultrasound to detect objects underwater
The sound wave is reflected off the ocean bottom
The time it takes for the sound wave to return is used to calculate the depth of the water
The distance the wave travels is twice the depth of the ocean
This is the distance to the ocean floor plus the distance for the wave to return
compression
when the longitudinal waves are packed together
rarefaction
when the waves are spread apart
wavespeed
how fast the wave travels to transfer energy
frequency
number of waves/time period
Sounds above 20,000 Hz are inaudible which are known as ultrasound
- prenatal scans
- cleaning jewellery
- submarines use it to see things around them (sonar)
- dog whistles
Sounds below 20Hz are inaudible and are known as
infrasound
Why do not all humans hear from the normal hearing range?
Because over time our hearing will become damaged.
Permanent hearing loss
When the hearing will remain damaged
temporary hearing loss
short term hearing loss,when you are ill, on a plane
What is an echo?
When sound hits hard objects we can hear echoes.An echo is when the sound bounces off hard objects.
speed of sound
340 m/s
Light
- it is a transverse wave
- these waves travel perpendicular to the direction of motion
- speed of light waves - 3x 10^8 m/s
Reflection
- It is when light hits smooth and shiny objects
reflection uses:
- mirrors
- Hivis jackets
angle of incidence=
angle of reflection
Refraction
- it is the bending of light when it changes optical density
- when light goes from less dense to denser it bends towards the normal line
- when light goes from denser to less dense it bends away from the normal line
