P5.1 Flashcards
What are waves
Waves are OSCILLATINIONS that transfer energy without transferring any matter.
Like when you strum a guitar, sound waves transfer energy but din’t take the air with the,, or else vacuum bruh.
Also waves modelled with ripples. Put small cork on surface, and you should see the transverse wave travels but water doesn’t.
What waves need medium to travel through and what are they called.
MECHANICAL WAVES, sound and water
Not electromagnetic
Difference between transverse and longtitufanal waves
How to get frequency’s, amplitude wavelength and time period
Ytanseverse waves vibrate a t 90 degrees to direction if th waves. (Energy still transferrred horizontallys .
Longtidunal waves vibrations are parallel to the direction of wave. Compressions and rarefactions.
Amplitude Rest to crest (high) or trough (low)
Wavelength (lamda) meters is distance from one point in a wave to distance on other point on wave. Also it would be one compression to other
Frequency is how many waves pass a point per second, measured in hertz
Time Period is 1/ f, it’s how long it takes for one wave to pass a point.
What are two ways to represent waves
What can you read from each graph?
Snap shot and time trice
Time trace is displacement over time, Snapshot is displacement over distance,
With time trace the distance from one point to other shows you time period . (Like how long it takes for a wave to pass a specific point)
Snapshot distance from one to other tells you the WAVELENGTH.
BOTH TELL YOU AMPLITUDE.
Which waves are transverse or longtidudnal
Transverse is ALL ELCTORMAGENTIC WAVES, AND WATER WAVES TOO
LONGTIDUANL IS SOUND WAVES (THINk areas of low and high pressure..
Therefore longtidunal)
Wave velocity equation (m/s)
= distance / time
Distance is wavelength, time is the time period , which is also 1/ frequency
Therefor = wavelength X 1/ frequency
Therefore wave speed= wavelength X frequency.
Change to hertz and meters.
How to measure wave velocity of sound waves in air.
PRACTICAL
1) time how long it takes to hear an echo of a clap from the wall, and then also measure the distance from the wall.
2) better way is to use oscilloscope attached to two microphones , and the oscilloscope will show you the time taken for the sound to pass through both microphone. Then use the wavelength which is distance of the two microphones and do the equations
2) different way, you move the microphones so that they are one wavelength away from each other in the oscilloscope- this ensures that the wavelength is true.
Then measure wavelength and use frequency of the signal generator producing sound to get wave speed.
3) with partner, one person use a pencil underneath the waves. One person draw ONE WAVES trajectory as it goes along. Another partner measures the time it takes for the wave to end.
Measure distance if pencil line, and time, and bruh
How to measure velocity if ripples (water waves)
Use a ripple tank nd a motor that causes waves at a fixed frequency.
1) to calculate wavelength, you use a strobe (flashing light). Adjust it so it’s at the right frequency where the light freezes the waves’ on a piece of paper bellow, then measure like 5 waves and calculate an average for wavelength
2) to calculate frequency, use the frequency of what every you set by the motor. Alternatively use a cork and a stopwatch, and count for say 30 seconds how many times the cork ‘bobs’ up and down. Then divide total bobs by time to get frequency, and find speed out. Or again you can see waves and count how many pass a point in 10 seconds, divide, etc
When waves travel from one medium to another, what stays the same?
FREQUENCY. The
Now you can Calu talge difference if speed etc
