Wave and Wave motion Flashcards
What are mechanical waves and give an example.
Waves must have a medium to travel through , vibrations are passed on from molecule to molecule. ex: water waves, sound waves
What are electromagnetic waves and give an example.
Waves do not need a medium to travel through and can travel through a vacuum. They travel fast at a speed of 3 x 10^8 m/s and travels fastest in a vacuum.
Ex: Radio waves, microwaves, x-rays
What are travelling waves
Waves that move from one place to another.
They transfer energy from the source to other places through which it passes
Explain how a compression wave on a spring works
Coils held together called compressions move along the spring. A stretched out region of coils called a rarefaction follows a compression along the spring.
What is a periodic travelling wave
Wave caused by the source repeatedly regularly moving
What is a transverse wave and give examples
Wave where direction of vibration i perpendicular to the direction the wave travels (up/down) ex: Water waves or waves on a rope
What type of waves are all electromagnetic waves
transverse
What is a Longitudinal wave and give examples
Wave where the direction of vibration is parallel to the direction which the wave travels (side to side)
Ex: compressions on a spring, sound waves in a medium
Explain crest
top of a wave
Explain trough
bottom of a wave
Explain amplitude and give it’s symbol
maximum distance of any particle from it’s undisturbed position (A)
Explain Oscillation
One crest and one trough- disturbance produced by one complete vibration of the source
Explain cycle
One crest and one trough- disturbance produced by one complete vibration of the source
Explain wavelength and give it’s symbol
distance from any point on one cycle to the corresponding point on the next (λ)
Explain velocity and give it’s symbol
distance travelled by one cycle in one second (c)
Explain frequency and give it’s symbol
number of cycles passing any point in one second (f)
What is the unit of frequency
Hertz (Hz) - 1 hertz is one cycle per second
Put a value to 1kHz
1,000 Hz
Put a value to 1MHz
1,000,000
Formula for frequency, wavelength and velocity
c=f(λ)
What is a phenomenon
an observable occurrence
What is reflection
Bouncing of waves off an obstacle in their path.
How do parallel waves reflect striking a flat obstacle?
Back at the same angle which they strike the obstacle
What is refraction
Changing of direction of a wave when it enters a region where it’s speed changes
What is the relationship between the speed, wavelength and frequency of a wave undergoing refraction
c=fλ so when wavelength increases wave speeds up and vice versa. Frequency stays the same
What is diffraction and give an example
Sideways spreading of waves into the region beyond a gap or around an obstacle. ex: sound waves undergo diffraction - we can hear around corners.
What is interference
When waves from two sources meet a new wave is produced. The displacement produced at any point by this wave is the algebraic sum of the displacements each waves produces on it’s own. This is interference of waves
What is constructive interference?
Waves from two sources meet and resultant wave’s amplitude is greater than the individual waves amplitude
What is destructive interference?
Waves from two sources meet and resultant wave’s amplitude is less than each of the individual waves amplitude
When does cancellation of waves occur with destructive interference
If crests from one source arrive at a point together with troughs of another source
What does completely out of phase mean with Interference
If one set is one half wavelength ahead of the other.
When is there a constant phase difference
When two sources emitting a definite fixed amount of step with each others waves
What is an interference pattern
When waves from two or more coherent sources meet the resulting pattern formed is called an interference pattern
Explain coherent sources
Two sources of periodic waves are coherent if they are in phase or have a constant phase difference between the waves of each source. If this is the case sources also have the same frequency.
Explain polarisation
The controlling of waves, Only transverse waves can be polarised. Transverse wave on a rope vibrating up and down is said to be vertically polarised. Only waves vibrating in a vertical plane pass through slit and others are unpolarised.
Explain plane of polarisation
Plane in which a transverse wave vibrates is it’s plane of polarisation
Explain Stationary
Two periodic travelling waves of the same frequency and amplitude moving in opposite directions meet, they interfere with each other. The resulting wave is formed is a stationary or standing wave
What are nodes
Points at rest
What are antinodes
Points vibrating at a maximum amplitude
How does a wave move in a stationary wave
Frequency of all vibrating particles is the same.
What is the distance between two consecutive nodes on a stationary wave?
λ/2
What is the distance between two consecutive antinodes on a stationary wave?
λ/2
What is the distance between an antinode and the next node on a stationary wave?
λ/4
What is the doppler effect
the apparent change in the frequency of waves due to the motion of the source or observer.
What is the symbol for observed frequency - Doppler effect
f’
When will f’ be greater than f
source is moving towards observer or vice versa
When will f’ be less than f
source is moving away from observer or vice versa
Give some application of doppler effect
microwaves in speed traps, red shift (stars), cars moving past you
What is the formula when source is moving towards the observer for the doppler effect
f’= fc/c-u
What is the formula when source is moving away from the observer for the doppler effect
f’= fc/c+u
What does u and c stand for in the doppler effect formula
u= speed of source c= speed o waves in a medium
