P5.1 Flashcards
What is a wave
A wave is a physical phenomenon that transfers energy WITHOUT TRANSFERRING MATTER.
Wave speed in the different states
Gas = particles far apart = vibrations passed on slowly = slow wave speed
Liquid = particles closer together = vibrations passed on faster = faster wave speed
Solid = particles very close together = vibrations passed on very fast = very fast wave speed
What is a longitudinal wave
Waves in which vibrations are PARALLEL to the direction of energy transfer/wave travel.
Eg. sound waves
Example of a longitudinal wave
Sound wave
What is a transverse wave
Waves in which vibrations are PERPENDICULAR to the direction of energy transfer/wave travel.
Example of a transverse wave
light / EM radiation
What is the normal line on a wave diagram
The mean position of a particle, about which it vibrates
What is the amplitude on a wave diagram
Maximum displacement of particles from their mean position
The bigger the amplitude the more ____ the wave carries
The bigger the amplitude the more ENERGY the wave carries
What is wavelength on a wave diagram
Distance from one peak (or trough) to the next peak (or trough)
What is frequency on a wave diagram
Number of peaks passing a point each second
How does wavelength effect frequency?
Bigger the wavelength, smaller the frequency
How are transverse waves represented on a wave diagram
peaks/troughs are perpendicular to the normal line
How are longitudinal waves represented on a wave diagram
Compressions = peaks
Rarefactions = troughs
What is a compression in a longitudinal wave
- particles squashed together
- high pressure
- peaks
What is a rarefaction in a longitudinal wave
- particles spread far apart
- low pressure
- troughs
EQUATION THAT IS NOT ON DATA SHEET BUT YOU NEED TO KNOW = RELATIONSHIP BETWEEN FREQUENCY AND TIME PERIOD
What is time period
The time taken to produce one wave / time it takes for one complete oscillation
Wave equation
Wave speed = frequency X wavelength
What is frequency measured in
Hz
Does wave velocity every change in the same medium
NOOOOOO
What can waves do
reflection(waves reverse direction)
… refraction(waves change direction/bend)
… diffraction(waves spread out)
Reflection/ refraction / diffraction can only happen at…
At the boundary between two media
What happens when a wave crosses a boundary
…..speed will change… FREQUENCY NEVER CHANGES
… wavelength will change
Reflection definition
Reflection is the wave phenomenon by which a wave reverses direction as it meets the boundary between two media.
Rules of reflection
“The angle of incidence, i is equal to the angle of reflection, r” i = r
What is a normal line on a RAY diagram
Intersects the mirror / lens BOUNDARY at exactly 90 degrees
What is an incident ray on a RAY diagram
Ray of light that comes towards the mirror
What is a reflected ray on a RAY diagram
Ray of light that moves away from the mirror, having interacted with the boundary
What is the angle of incidence
Angle incident ray makes with normal
What is the angle of reflection
Angle the reflected ray makes with the normal
How to draw a ray diagram for a image formed in a mirror
You need 2 incident rays from the object.
You then project the 2 reflected rays back into the mirror.
Refraction definition
Refraction is the wave phenomenon by which a wave changes direction (bends) as it crosses the boundary between two media.
How does refraction work
As waves cross a boundary between two different media…
… their speed changes…
… their direction changes…
… they are observed to bend.
Draw an example of a refraction ray diagram on a glass cube - use the air-glass boundary
What happens if a wave passes from a less dense medium to a more dense medium
Waves bend TOWARDS THE NORMAL when they pass from less dense to more dense medium + they slow down
What happens if a wave passes from a more dense medium to a less dense medium
Waves bend AWAY FROM THE NORMAL when they pass from more dense to less dense medium + when they speed up
What is an ultrasound
is the name given to sound waves with a frequency greater than 20,000Hz.
What are ultrasound scans used for
used to image a baby inside a womb as well as detecting cracks in metal pipes and buildings.
How does an ultrasound scan work
- The transducer is a device that produces ultrasound waves by causing a crystal to vibrate very rapidly.
- The ultrasound waves are partially reflectedevery time they cross a boundarybetween different media.
- The reflected ultrasound waves return to the transducer as a series of pulses, which are deciphered to form an image.
What is the first recorded pulse on a oscilloscope trace
The first recorded pulse is always the reflection of the transmitted pulse as it crosses into the body.
Depth of boundary formula
Depth of boundary= (speed of the ultrasound waves) x (transit time) x ½
The oscilloscope beam takes 32 millionths of a second to travel across each grid square on the screen.
How long does each pulse take to travel to its reflecting boundary?
What is the distance from the body surface to the nearest boundary? The speed of ultrasound in the body is 1500m/s.
What happens if the light passes through the normal line like this
Whenever light passes between media along the normal line, IT DOESN’T REFRACT…
… passes straight through
How does the ear detect sound
- The pinna and auditory canal gather the sound wave; direct sound into the ear drum
- The ear drum vibrates, and causes the ossicles to vibrate; vibrations of sound wave amplified
- Cochlea transmits vibrations to small hairs
- Hairs are attached to sound-detecting cells;
- Cells release chemicals when stimulated, electrical signal sent to brain via auditory nerve
What is the ear designed to do
to detect, amplify and convert sound to an electrical signal.
What does the pinnacle and auditory canal do
gather the sound wave; direct sound into the ear drum
What does the cochlea do
transmits vibrations to small hairs
What is a natural frequency of an object
natural frequency of an object is the frequencyat which it can (physically) vibrate.
Why does the human ear have an Audible range
The human ear drum can only vibratebetween 20Hz and 20,000Hz…… it is unable to vibrate any slower or faster than these limits.
Thus, the human audible range is only 20hz-20,000Hz
