Waves Flashcards
What’s an oscillation?
When the particle in a wave moves backwards and forwards or up and down yet returns to the starting position however the wave itself moves forwards
What are the two types of wave and give some examples of each
Longitudinal- sound,seismic P waves and pressure waves
Transverse - light, sea waves,seismic S waves and Mexican waves
What are transverse waves?
The wave oscillates perpendicularly the direction of the motion
What angle do each part of the wave move at in a transverse wave?
90 degrees to the direction the energy is moving in
Describe a longitudinal wave
The wave moves in the same direction as the direction the energy is going, they move in a plane parallel to the direction of the wave
What is a pressure wave?
When you speak to somebody and the air vibrates in longitudinal waves
What is amplitude?
The maximum displacement of a wave from its rest position measured in metres (linked with volume)
What is wavelength?
The distance between two peaks and two crests measured in meters
What is frequency?
The number of oscillations/vibrations per second (linked with pitch)
What unit is frequency measured in?
Hertz (hz)
If a wave can travel through a substance the wave is what?
Transmitted through it
What does opaque, transparent and translucent mean?
Opaque - completely not see through
Translucent - partly see through
Transparent- completely see through
In a vacuum what speed does EM waves travel at?
The speed of light (they are transverse waves)
The higher the frequency the higher the e…
Energy of the wave
What is the only difference between electro magnetic waves?
Frequency and wave length
What is the spectrum?
Each colour corresponds to a different wave length
Where are violet and red on the spectrum?
Red - the longest - refracted the least in a prism
Violet - the shortest - refracted the most in a prism
What are the primary and the secondary colours of light?
Primary colours - Red, green , blue
Secondary colours - magenta, cyan and yellow
What do filters do?
They absorb all colours and don’t posses and transmit those that do
What do surfaces do?
They absorb all colours and do not posses and reflect those that do
What do surfaces do?
They absorb all colours and do not posses and reflect those that do
WHen do objects emit radiation?
Due to their temperature - the higher the temperature the greater the amount of infrared emmited
When can an object emit visible light?
When it gets hot enough
What does infrared cause!?
Causes heat - exposure to small a,lungs warms a person (e.g sunlight)
What does large amount exposure to infrared radiation cause?
Burns
What does ultraviolet light cause?
- tanning UV
- materials to fluorescence (shine with visible light)
What could ultraviolet light be used for?
To detect forgeries on bank notes
What are the three main categories of ultra violet radiation and their properties
- UVA - longest wave length, tanning, 99% UV light to reach the earth
- UV B - medium wave length, damages cells, causes sunburn and skin cancer
- UV C - shortest wave length, the most damaging, filtered out by earths ozone layer
What type of waves can be reflected?
All
What’s the normal?
An imaginary line drawn at 90 degrees to the mirror
What’s an incident ray?
When the ray hits the mirror and goes IN the mirror
What’s a reflected ray?
When the ray leaves the mirror
How do you measure the angle of incidence?
Between the normal and the incidence ray
How do you measure the angle of reflection?
.
It’s measured between the Normal and the reflected ray
What’s the law of reflection?
The angle of incidence = the angle of reflection
When do sound and light waves change speed?
When they pass between the boundaries of two different substances with different density’s
What is refraction the change of?
Direction
At what speed will the light move through a more dense substance?
Slower speed
What’s superposition?
When waves meet with each other they create an interference pattern
High frequency’s =…
High pitch
What is the human hearing range?
Between 20 Hz - 20,000
What does the amplitude tell us?
The volume - its an indicator of how much energy is transferred
What’s volume measured in?
Decibels (dB)
Hard surfaces _______ , soft __________ it
Reflect sound, absorb
Flat surfaces ________ , rough _________ it
Reflects sound, scatters
What does the electrical current cause the solenoid to become?
Magnetised
Since the solenoid is in a magnetic field what happens?
The solenoid experiences a force
What causes the magnetic force to either move the solenoid out or into the permanent magnet, due to the change in direction of the force?
Alternating current
What does the diaphragm in a speaker do?
Moves the solenoid which causes air molecules near the diaphragm to vibrate
What causes the flexible membrane to vibrate back and forth?
The sound wave
How is the small electrical current in microphones caused?
The solenoid is moved forwards and backwards through the magnetic field
Why does the direction of the electrical current change?
The vibration of the solenoid changing direction
Since the signal is weak what needs to be happened in microphones to be used in a loudspeaker?
It needs to be amplified
