Waves - Properties Flashcards
What is a wave?
Wave is a method of transferring ENERGY through a medium, without the medium moving from the rest position itself.
Eg:
- we can see because of the energy carried by a light
- our ears use the energy from sound waves in a way allowing us to hear
What are the two main types of waves?
- Electromagnetic
- Mechanical
What is the difference between a mechanical wave and an electromagnetic wave?
A mechanical wave NEEDS a medium to travel through whereas electromagnetic waves can have a medium, but DO NOT NEED the medium to travel through.
Why do mechanical waves need a medium to travel through?
Because the creation of the wave is due to the physical movement of the medium.
eg
water waves - need water to travel through
sound waves - travels mostly through air, but can travel through liquid or solid.
earthquake waves - need rock to travel through
After the mechanical wave passes through, the medium is left in the same position before the wave had arrived.
Electromagnetic waves
- Radiowaves
- Microwaves
- Infrared waves
- Light waves
- Ultraviolet waves
- X-rays
- Gamma rays
How are waves generated in a medium?
To generate a wave in a medium, the medium has to be disturbed in some way.
eg:
- An earthquake is generated when pressure builds up between 2 tectonic plates until one slips against the other.
- In the ocean, the wind whipping against the surface of the water generates ocean waves
- When a guitar is plucked it is the vibration of the guitar string that sends a sound wave through the air.
What is amplitude?
The maximum displacement between rest position and a peak/trough. The maximum distance the medium goes out, in either direction, from its middle position.
Half the distance between a crest and a trough
What is wavelength?
The distance between two identical points on adjacent waves. Most conveniently measured from peak to peak or trough to trough.
What is the relationship between energy and amplitude?
The MORE energy used to create the wave, the GREATER the amplitude.
For example,
- the GREATER the amplitude of a sound wave, the more energy it is carrying therefore the LOUDER the sound.
- The GREATER the amplitude of a light wave, the more energy it is carrying therefore the BRIGHTER the light.
What is the relationship between frequency and wavelength?
The GREATER the frequency, the SMALLER the wavelength.
higher frequency = more waves per second, shorter wavelength = more waves
What is the local effect of a mechanical wave in the medium?
The medium does not move apart from the local disturbance which is the passage of the wave itself.
The local effect of the wave on the medium is to make EACH POINT in the medium complete ONE FULL SWING. (out and back in one direction followed by out and back in the other direction). The point in the medium is now back to where it started from.
What is the difference between a transverse and a longitudinal wave?
- The wave is TRANSVERSE if the local movement of the medium is PERPENDICULAR to the direction in which the wave is travelling.
- The wave is LONGITUDINAL if the local movement of the medium is PARALLEL to the direction in which the wave is travelling.
What is frequency on both longitudinal and transverse waves?
The frequency is the number of waves produced per second.
- On a transverse wave, the frequency is the number of crests/troughs of the medium that pass a point every second
- On a longitudinal wave, the frequency is the number of compressions in the medium that pass a point every second
What is frequency measured in?
Hertz, Hz
What is the period of a wave?
The time taken for one complete wave. eg two adjacent crests/troughs to pass a point.
