Topic 4:Waves And Electromagnet Flashcards
What do all waves transfer?
Energy and information from one place to another
What do waves not transfer?
Matter!
What are the 2 types of wave?
Transverse and longitudinal
What does a transverse wave do?
Used to show wave length and amplitude
How do the particles in a transverse wave move?
Each particle moves at a 90° angle, perpendicular to the direction of motion
Examples of transverse waves
Sea waves, secondary earthquake waves
What do longitudinal waves show?
Show areas of compression and refraction
How do the particles in longitudinal waves move?
They can oscillations parallel(in the same direction) to the direction of motion
Examples of longitudinal waves
Sound
What is the frequency and what’s the measurement?
Number of waves passing a point each second, measure in Hz
What does wavelength mean and measurement?
Distance from one point on a wave to the same point on the next wave, m
What is the amplitude and measurement?
Distance from the middle of the wave to the the top or bottom, m
What is the period and measurement?
The length of time it takes one wave to pass a certain point, seconds
What is the velocity and measurement?
The speed of a wave in the direction it’s travelling, m/s
What happens if the frequency increases?
The wavelength decreases
High frequency =?
Higher pitch
What is the equation for speed?
Speed = distance/time
What is the equation for wave speed?
Wave speed(m/s) = frequency(Hz) X wavelength(m)
What is refraction?
The bending of a wave when it enters a medium where it’s speed is different
What depends on the density?
The medium changing the speed of the wave
Where is the normal line?
At 90° angle to the interface
The higher the density =?
The slower the wave travels
Normal =?
Perpendicular to the surface
Less dense means?
Away from the normal
More dense means?
Towards the normal
What happens to the frequency?
It always stays the same
If the speed increases what happens to the wavelength?
It increases
What is an example of a water wave that shows the particles vibrate and transfer information but don’t move
If u drop a twig into a calm pool of water, ripples form on, and move across the waters surface, the ripples don’t carry the water or the twig away from them tho
What is an example of a sound wave that shows the particles vibrate and transfer information but don’t move
If u strum a guitar string and create a sound wave, the sound wave travels to your ear but it doesn’t carry the air away from the guitar
What does an oscilloscope measure
The speed of a sound
Steps of using an oscilloscope to measure the speed of sound
1) set up the oscilloscope so the detected waves at each microphone are shown as separate waves
2) start with both microphones next to the speaker, then slowly move one away until the 2 waves are aligned on the display but have moved exactly 1 wavelength apart
3) measure the distance between the microphones to find 1 wavelength
4) use the formula velocity=wavelength x frequency to find the speed of the sound waves passing thru the air - frequency is whatever u set the signal generator to in the first placem
What do u use to find the wavelength of sound waves generated
2 microphones and an oscilloscope
What do u use to measure the speed of water ripples
A strobe light
What are the steps to measuring thr speed of water ripples using a strobe light
1) using a signal generator attached to the dipper of a ripple tank u can create water waves at a set frequency
2) dim the lights and turn on the strobe light - you’ll see a wave pattern made by the shadows of the wave crests on the screen below the tank
3) alter the frequency of the strobe light till the wave pattern freezes - when frequency of strobe light and wave are =
4) distance between each shadow line is equal to 1 wavelength. Measure the distance between lines that are 10 wavelengths apart = average wavelength
5) calc speed of the waves
How do u find the speed of waves in solids
Use peak frequency
How do u use peak frequency to measure the speed of waves in solids
1) measure and record the length of a metal rod e.g. brass rod
2) set up apparatus with clamp, elastic bands hammer, microphone, rod. Make sure to secure the rod at its centre
3) tap the rod with the hammer. Write down the peak frequency displayed by the computer
4) repeat this 3 times to get an average peak frequency
5) calc the speed, wavelength = twice length of the rod
What 3 things can happen when a wave meets a boundary
Can be absorbed by the 2nd material, transmitted thru the 2nd material or reflected
What does it mean if the wave is absorbed by the 2nd material
The wave transfers energy to the materials energy store often the energy is transferred to a thermal energy store which leads to heating
What do3s it mean if the wave is transmitted thru the 2nd materia
The wave carried on travelling thru the new material this often leads to refraction this can be used in communications as well as in the lenses of glasses and cameras
What happens when a wave crosses a boundary between different materials
It changes speed
What happens if the wave hits the boundary at an angle
This change of speed causes a change in direction-refraction
What type of waves are electromagnetic waves
Transverse
What speed do electromagnetic waves travel through a vacuum
The same speed
What do all EM waves transfer and e.g.
Energy from a source to an absorber, e.g. when u warm yourself by an electric heater, infrared waves transfer energy from the thermal energy store of the heater(source) to your thermal energy store(absorber)
What is the order of EM spectrum
Radio waves, micro waves, infrared, visible light, ultra violet, X-rays, gamma rays
What does the higher the frequency of the EM wave mean
The more energy it transfers so the more dangerous for humans
What are the harmful effects on humans of microwaves
Internal heating of body cells
What are the harmful effects on humans of infrared
Skin burns
What are the harmful effects on humans of UV rays
Ionising radiation - damages surface of cells and eyes leading to skin cancer and eye conditions
What are the harmful effects on humans of x-rays and gamma rays
Mutation or damage to cells in the body
Uses of radio waves
Broadcasting, communications, satellite transmissions
Uses of microwaves
Cooking, communications, satellite transmissions
Uses of infrared
Cooking, thermal imagery, short range communications, optical fibres, television remote controls, security systems,
Uses of visible light
Vision, photography, illumination
Uses of ultra violet
Security marking, fluorescent lamps, detecting forged bank notes, disinfecting water
Uses of x-rays
Observing internal structure of objects, airport security scanners, medical x-rays
Uses of gamma rays
Sterilising food and medical equipment, detection of cancer and it’s treatment
What can radio waves be produce by and induce
Oscillations in electrical circuits
What can changes in atoms and nuclei do
Generate radiation’s over a wide frequency range, be caused by absorption of a wide range of radiations
How are EM waves grouped
Based on their wavelength and frequency
What are EM waves made up of
Oscillating electric and magnetic fields
