Section 3 - Waves And The Electromagnetic Spectrum Flashcards
What do waves transfer?
Energy
Information
What do particles in a wave do?
Vibrate
What is the amplitude of a wave?
The displacement from the rest position to the trough or the crest
What’s the wavelength of a wave ?
The wavelength of a wave is length of a full cycle of the wave
Distance between 2 identical points
What’s the frequency of a wave ?
What’s frequency measured in?
The frequency of a wave is Number of complete cycles of the wave passing a certain point per second.
Frequency is measured in hertz(hz)
1hz is one wave per second
What’s the period of a wave?
How do we calculate the period of a wave?
The period of a wave is the number of seconds it takes for a full cycle of a wave to pass a certain point
Period= 1/frequency
What type of vibrations do transverse waves have?
Real life example of one
The vibrations are perpendicular to the direction a wave travels
A spring wiggled up and down gives a transverse wave.
Examples of transverse waves …
- all electromagnetic waves
- S-waves ( a type of seismic wave)
-ripples and waves in Water
The vibrations in a longitude wave …
What do they do as they travel through a medium?
What does this cause?
In longitudal waves, the vibrations are parallel to the direction of travel of the wave
They squash up and stretch out the arrangement of particles in the medium as they pass through.
This makes compressions (high pressure) and rarefractions ( low pressure)
Examples of longitudal waves…
Sound waves
P-waves
What is wave speed?
Wave speed is how quickly a wave moves through a place
2 ways to calculate wave speed?
Wave speed = distance/time
Wave speed=frequency(Hz) X wavelength (m)
Equipment to measure the speed of sound?
oscilloscope
Signal generator
Two microphones
Speaker
How do we measure the speed of sound?
-Set up the oscilloscope so the detected waves at each microphone are shown as separate waves
-start with both microphones next to speaker then move one away until two waves are aligned on the display but have moved one wavelength apart
-measure distance between the microphones to find one wavelength
-use the formula v= frequency X wavelength to find the speed of sound waves passing through the air
How to measure the speed of water ripples using a strobe light ?
1)Using a signal generator attached to the dipper of a ripple tank create water waves at a set frequency.
2)dim lights and turn on a strobe light. You’ll see a pattern of waves below
3) alter the frequency of the strobe light until the wave pattern on the screen appears to freeze and stop moving. This happens when the frequency of the waves and the strobe light are equal
4) the distance between each shadow line is equal to one wavelength. Measure distance between lines that are 10 wavelength apparent then find avaradhe wavelength
5) use v=frequency X wavelength to find the speed of the waves.
How do we find speed of waves in a solid ?
Measuring the frequency of sound waves produced when you hit the object
Hitting the rod causes waves to be produced along the rod
These make the rod vibrate and produce sound waves in the air around the rod
These sound waves have the same frequencies as the waves on the rod
Method of finding wave speed in a solid…
1) measure and record the length of a metal rod
2) set up apparatus. Rod attached to clamps by elastic bands, microphone attached to computer on the left of the rod. Hammer on the right of the rod
3) tap the rod with the hammer. Write down the peak frequency displayed by the computer
4) repeat this three times to get an avaradhe peak frequency
5)calculate speed of the wave by using v=frequency X wavelength. The frequency is represented as the rod length X 2
What can waves do at boundaries ?
Be absorbed
Reflected
Transmitted
Refracted
What happens when a wave is absorbed at a boundary?
The wave transfers energy to the materials energy stores
What happens when a wave is transmitted at a boundary ?
The wave carries on travelling through the new material. This often leads to refraction. Refraction can be used in communications
What does what happens to a wave as it reaches an interface depend on?
Wavelength
Properties of the material involved
What can happen at a boundary causing a wave to refract?
The wave changes speed
What happens if the wave hits the boundary at an angle?
The change in speed will cause a change in direction- refraction
What happens in the wave is travelling along the normal ?
The wave will change in speed but not be refracyed