Topic 6 - Waves Flashcards
(44 cards)
Describe transverse waves
The vibrations are perpendicular to the direction of energy transfer
e.g water waves
Describe longitudinal
The vibrations are parallel to the direction of energy transfer
e.g sound waves
Define time period
the time taken for a particle to complete one vibrational cycle
Define frequency
the number of complete waves every second (measured in hertz)
Time period =
1 / frequency
Define wave speed
the speed at which energy is being transferred
Wave speed =
frequency x wavelength
Describe how you would use a ripple tank to measure the speed of waves
- set up the ripple tank, put a large sheet of card under the tank on the floor and pour about 5mm of water into the tank
- put the wooden rod so it just touches the surface of the water
- switch on the overhead lamp and motor and adjust so the waves are low frequency and you can see it clearly on the card
- place a meter ruler on the card, measure across as many waves as possible and divide that length by the number of waves (gives the wavelength)
- count the number of waves passing a point in 10 seconds and divide by 10 (gives the frequency)
- calculate wave speed using wave speed = frequency x wavelength
Describe how you would calculate the wave speed on an elastic cord
- set up a vibration generator, power supply, elastic cord, masses and a hanger, a wooden bridge and pulley on a clamp
- turn on the vibration generator
- use a meter ruler to measure as many half wavelengths as possible, then divide total length by the number of half waves then times by 2 (gives the wavelength)
- frequency is the frequency of the power supply
- use wave speed = frequency x wavelength
What is the law of reflection?
angle of incidence = angle of reflection
What 3 things could happen when a wave arrives at an interface (boundary between 2 mediums)?
- absorbed
- transmitted (continue travelling)
- reflected
Describe the angle of incidence
the angle between the incoming ray and the normal
Describe the angle of reflection
the angle between the reflected ray and the normal
Reflection produces a _____ image.
virtual
What is specular reflection?
- happens when a wave is reflected in a single direction by a smooth surface
What is diffuse reflection?
- happens when a wave is reflected by a rough surface and the reflected rays are scattered in lots of directions
What is refraction?
when light passes from one medium to another with a different optical density, the light changes direction
Describe how to investigate refraction
- place a transparent rectangular block on a piece of paper and trace around it
- use a ray box to shine a ray of light in the middle of one side of the block and trace the incident ray and emerging ray
- remove block and join up the lines to show the path of the refracted ray
- draw the normal where the light ray entered the block and use a protractor to measure the angle of incidence and the angle of refraction
- repeat experiment with different materials of block
Describe how to investigate reflection
- draw a straight line on a piece of paper and place an object so its side lines up
- shine a ray of light at the object and trace the incoming and reflected light beams
- draw the normal where the ray hits the object
- use a protractor to measure the angle of incidence and reflection, and make note of the width and brightness of the reflected ray
- repeat with different objects
Define electromagnetic waves
Transverse waves that transfer energy from the source of the waves to an absorber
All electromagnetic waves are …
- transverse
- can travel through a vacuum
- all travel at the same speed in a vacuum
Name the 7 types of electromagnetic waves, starting with the low energy
- radio waves
- microwaves
- infrared
- visible light
- ultraviolet
- x-rays
- gamma rays
Describe the red end of the EM spectrum
- lower energy
- long wavelength
- low frequency
Describe the violet end of the EM spectrum
- higher energy
- short wavelength
- high frequency
