6. Waves Flashcards
What type of wave is a sound wave?
Longitudinal
Which type of vibrations move parallel to the direction of the wave?
Longitudinal
Which type of vibrations move perpendicular to the direction of the wave?
Transverse
Which waves can’t travel through a vacuum?
Mechanical
Which waves can travel through a vacuum?
Electromagnetic
Which waves pass their vibrations through particles?
Mechanical
What is frequency measured in?
Hertz
If one wave passes per second, what is the frequency?
1 Hz
How do you work out frequency?
Frequency = 1 / Period
What is a period?
How long is takes for the wave to pass a point - messed in seconds
Equation for wave speed?
Wave speed = frequency x wavelength
Equation for frequency?
Frequency = speed / wavelength
Equation for wavelength?
Wavelength = speed / frequency
What is the symbol for wavelength?
Lambda
What does the angle of incidence equal?
The angle of reflection
When light enters a glass cube, which direction does it refract?
Towards the normal
What happens when light enters a denser glass block?
The speed of the wave decreases and it refracts towards the normal
When the incident ray leaves the glass block, which direction does it go in?
Away from the normal
What happens to the speed of the ray it leaves the glass block?
It speeds up and bends away from the normal
What is the speed of a wave through a vacuum?
300,000,000 or 3x10 to the power of 8
Do different electromagnetic waves carry different amount of energy?
Yes
What happens when a ray is absorbed instead of reflected?
It heats up
What happens as the energy of a wave increases?
The temperature and hazard increased
What happens as the wavelength decreases?
The frequency increases The energy carried increases The waves become more dangerous The waves diffract less The waves have a shorter range The waves carry more information
What are the groups in the electromagnetic spectrum?
Gamma X-ray Ultraviolet Visible Infrared Microwaves Radio waves
What type of electromagnetic wave has the highest frequency and energy, and the shortest wavelength?
Gamma
What type of electromagnetic wave has the lowest frequency and energy, and the longest wavelength?
Radio waves
What are infrared waves used for?
To locate fire, detect humans and night vision
What type of wave is a light wave?
Transverse
What are radio waves used for?
Radio, TV, telecommunications
What are gamma waves used for?
Kills bacteria, radiotherapy, cancer treatment
What are microwaves used for?
Radar detection, satellite communications, cooking
What are in X-rays used for?
Examine damaged machinery and medical scans
What are visible waves used for?
Computers, TV, LED display, to see
What are ultraviolet waves used for?
Detect counterfeit banknotes
What are the hazards of infrared waves?
Overheating - burning
What are the hazards of radio waves?
None
What are the hazards of gamma waves?
Cancer mutations to tissue
What are the hazards of microwaves?
Damage parts of brain
What are the hazards of X-Ray’s?
Body cells can be killed by high doses
What are the hazards of visible waves?
Intense beam damages eyes
What are the hazards of ultraviolet waves?
Sun burn, skin cancer
How are sounds made?
When an object vibrates and it causes the layer of air next to it to vibrate
Where do sounds travel fastest? Why?
Solids because the particles are closer together
Why is the no sound in a vacuum?
Because there are no particles to vibrate and pass on energy
What do you need to remember when doing f=v/lambda
MAKE SURE THAT THE WAVELENGTH IS IN METRES, THE TIME IN SECONDS AND FREQUENCY IN HZ
What is the range of normal human hearing?
20Hz to 20,000Hz
When will sound waves refract?
When air changes temperature (change in medium) - waves will travel slower in cooler air
Where does sound refract in the night?
Downwards, the air near the ground is cooler than the air higher up
What frequency are ultrasound waves?
Higher than 20,000Hz
What is ultrasound used for?
Medical
Industrial cleaning and no destructive testing of materials
Why does the ultrasound need to be a pulse?
So you can hear the echo
How is the time delay for an ultrasound and pulse worked out?
distance = speed x time
Why is gel used in ultrasound?
Because then there is more ultrasound absorbed. When there is a big difference between densities lots of it would be reflected.
What is the distance in ultrasound?
The way there and back
What is the depth in ultrasound?
Just the way there
Other uses of ultrasound?
The detection and removal of kidney stones
What makes seismic waves?
A sudden release of energy in the earths crust
What is used to detect movements of the earths crust?
A seismometer
What are the two types of seismic wave?
Primary and secondary
Properties of primary waves?
- longitudinal
- travels through solids and liquids
- travels faster
Properties of secondary waves?
- transverse
- only travel through solids
- travels slower
Where does the sun’s spectrum peak?
At visible wavelengths
