Waves (2) Flashcards
Transverse waves and their structure
oscillations are perpendicular to the direction of energy transfer
examples- em waves, ripples in water, a wave on string
amplitude- distance from top or bottom to baseline
wavelength- the distance between the same point on two waves
trough- bottom
crest- top
Longitudinal waves structure
oscillations are parallel to the direction of energy transfer
areas of compression and rarefaction
examples- sound waves, seismic waves
wave speed-
frequency-
period-
wave speed- how fast the wave is moving
frequency- the number of waves passing past a point in a given time
period- the time taken for one complete wave cycle
waves on string RP
attach one end of the string to a vibration generator and the other over a pulley with weights to maintain tension.
Connect the vibration generator to a signal generator to control the frequency
Adjust the frequency until a standing wave forms
Count the number of loops (each loop is half a wavelength)
Use a ruler to measure the total length of the loops.
Divide total length by number of half wavelengths, then times by 2
Calculate wave speed using the wave equation:
Ripple tank RP
Set up the ripple tank with water and a light source to project wave patterns onto the screen.
Turn on the vibrating dipper to produce regular waves at a set frequency
Measure the wavelength by placing a ruler next to the tank and taking a photo, then measure the distance between 10 waves, then divide this by 10
(or do a slo-mo video and count 10 waves passing a point then divide by 10)
use equation to calculate wavespeed
Using an Oscilloscope to measure the speed of sound
- attach a signal generator to a speaker to generate sounds with a specific frequency
- set up oscilloscope so that the detected waves at each microphone are shown as separate waves
- start with both microphones next to the speaker, then slowly move one away until the two waves are aligned
- measure the distance between the microphones to find the wavelength
- use equation to find speed (330 m/s)
specular reflection
when a wave is reflected in a single direction off of a smooth surface
angle of incidence = angle of reflection
surfaces are shiny with clear reflections
diffuse reflection
waves are reflected by a rough surface and are scattered in lots of different directions
this happens when the normal is different for each incoming ray
reflections appear matte and you don’t get a clear reflection
Electromagnetic spectrum and their properties
radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, gamma rays
transverse waves
travel at the same speed through air or a vacuum
wavelength increases going down the spectrum, frequency decreases
what is refraction
what happens if a wave hits the normal
a wave changing speed and therefore direction through a boundary because of the change in material density
if the wave travels along the normal there will be a change of speed but no directional change
Refraction through glass block RP
Place the glass block on a piece of paper and draw around it.
Shine a ray of light from the ray box at an angle towards one side of the block.
Mark the incident ray, the refracted ray inside the block, and the emerging ray on the paper.
Remove the glass block and use a ruler to draw the complete path of the light ray.
Measure the angle of incidence and the angle of refraction using a protractor.
Repeat for different angles of incidence.
reflection on mirror RP
- Place the mirror on a piece of paper and draw a straight line to mark its position.
- Draw a normal line at the point where the light ray will strike the mirror.
- Shine a ray of light from the ray box towards the mirror at an angle.
- Mark the incident ray and the reflected ray
- Remove the mirror and use a ruler to draw the complete path of the light rays.
- Measure the angle of incidence and the angle of reflection using a protractor.
- Repeat for different angles of incidence.
how are radio waves generated
uses
A radio transmitter generates an alternating current , which passes into an aerial
The electrons oscillate, creating radio waves that spread out into space
the frequency of the wave produced is equal to the frequency of the AC
When the radio waves reach a receiving aerial, they cause the electrons to oscillate, generating an alternating current.
This alternating current has the same frequency as the transmitted wave.
The signal is then decoded into sound or data.
Microwaves uses (2)
Microwaves are absorbed by water molecules in food
The energy causes the molecules to vibrate more, increasing their kinetic energy and heating the food around it
Microwaves pass through the Earth’s atmosphere without being absorbed or scattered.
Signals are sent from a ground station to an orbiting satellite and then re-transmitted back to Earth.
Used for TV broadcasts, mobile phone networks, and GPS.
Infrared radiation
how is it detected
uses
infrared radiation is given off by hot objects
Infrared cameras detect heat emitted by objects and convert it into a visible image
Grills, toasters, and ovens use infrared radiation to directly heat food.
Infrared heaters warm objects and people without needing to heat the surrounding air.
Fibre optic cables
cables made of glass or plastic that can carry large amounts of data over long distances using visible light
they work by the light waves reflecting back and forth off of the glass fibres
the light isn’t easily absorbed so no data is lost as the signal isn;t scattered so the cables are extremely fast
What is fluorescence
UV light uses
fluorescence is where UV light is absorbed and visible light is emitted
UV radiation gives suntan
UV can be used to detect fake currencies
Fluorescent lighting
Uses of xrays
x-rays pass through flesh but not bone so can provide medical imaging of bone structures
Uses of gamma rays (2)
Gamma rays can be used in radiotherapy to treat cancer by killing the cancerous cells
It can also be used as a medical tracer
Risks of EM radiation
Radiation can cause ionisation of cells, which can lead to cancers. This is why it must be used safely in medical procedures
concave lenses
what type of image do they form
Concave Lenses
Thinner in the middle and thicker at the edges (diverging lens).
The focal point is on the same side of the lens as the object where the rays hitting the lens parallel to the axis come from
Forms virtual, upright, and diminished images (when the object is placed beyond the focal point).
Always forms a virtual image for objects closer than the focal length.
convex lenses
type of image formed
Convex Lenses
Thicker in the middle and thinner at the edges (converging lens).
The focal point is on the opposite side of the lens to the object and is where rays hitting the lens parallel to the axis all meet
Forms real, inverted, and diminished images (when the object is beyond 2F).
Can form both real and virtual images, depending on object distance from the lens.
How are Convex ray diagrams drawn
rules:
Draw a line from the top of the object to the lens parallel to the axis
Draw another ray from the top of the object going through the centre of the lens
The first ray then crosses through the focal point on the other side of the lens
The ray that passes through the centre doesn’t refract
Where the rays meet is where the image is formed
Beyond 2F → Real, inverted, diminished
At 2F → Real, inverted, same size
Between F and 2F → Real, inverted, magnified
At F → No real image
Between F and O → Virtual, upright, magnified
How to draw Concave ray diagrams
image formed properties:
Draw a line from the top of the object to the lens parallel to the axis
Draw another ray from the top of the object going through the centre of the lens
Draw a dotted line from the focal point before the lens to the incident ray
The image is formed where the two rays meet
Concave lenses always form virtual, upright, diminished objects
