Longitudinal Waves
What is the distance between 2 compressions called?
Wavelength
What is the distance from crest to crest called?
wavelength
If you increase the amplitude of the sound waves, how do you hear the sound differently?
Louder, amplitude = volume
If you increase the amplitude of the light waves, how do you see the sound differently?
The light is brighter, amplitude = brightness
A star is moving towards us. What kind of shift would you expect?
A blue shift
What is the length of the compression called?
Amplitude
What is half the distance from trough to crest called?
Amplitude
If you increase the frequency of the sound waves, how do you hear the sound differently?
Higher pitch, frequency = pitch
If you increase the frequency of the light waves, how do you see the light differently?
The light changes colors and shifts towards the violet end of the spectrum as frequency of light equates to color.
A star is moving away from us. What kind of shift would you expect?
A red shift
Give an example of a longitudinal wave and what it needs to travel in.
Sound and must travel through air.
Give an example of a transverse wave and what it needs to travel in.
A police car races towards you with its siren on. How do you hear the siren change as it approaches you?
An astronomer notices that a newly discovered star has its star is blue-ish. The astronomer compares that to a well known star, Bernard which is red. Which star is hotter and how you know?
The new star is hotter because it burns blue which has more energy than red.
Mr. G will show you a star spectra problem
See board for answer
In a longitudinal wave, what direction do the particles travel?
Parallel to the direction the wave travels
In a transverse wave, what direction do the particles travel?
Perpendicular (90 degrees) to the direction the wave travels
An astronomer is testing the Doppler effect using a sound-emitting probe that travels through Earth's atmosphere toward a stationary detector. The probe emits a steady tone of 800 Hz. The detector measures a frequency lower than 800 Hz, even though the probe is moving. What must be true about the probe's motion relative to the detector, and how would the detected frequency change if the probe reversed direction and approached the detector?
Probe must be moving AWAY from the astronomer as it has a lower pitch.
An astronomer notices that a newly discovered star has its star spectra shifted towards the blue end of the spectrum. What can the astronomer infer about the newly discovered star?
Since it is blue shifted the astronomer knows that the star is moving towards us.
Mr. G will show you star spectra problem
See board for answers.
Draw a longitudinal wave and label the:
1) compressions
2) rarefactions (stretching)
3) wavelength
4) amplitude
see board for model
Draw a transverse wave and label the:
1) crest
2) trough
3) wavelength
4) amplitude
see board for example
Two students investigate the Doppler effect. In Experiment 1, a student stands still while a friend rides a bicycle toward them, sounding a horn at a constant frequency. In Experiment 2, the friend stands still and sounds the same horn while the student rides a bicycle toward them at the same speed. Both experiments take place in still air. Assuming the same relative speed, which student hears the higher frequency, and why?
They BOTH hear the same thing because it doesn't matter who is moving. In both experiments they are moving towards each other decreasing the wavelengths, increasing the frequency, and thus leading to higher pitches.
Astronomers observe two stars that have the same surface temperature, but their spectra show the same absorption lines at different wavelengths. Star A’s lines are shifted toward the red end of the spectrum, while Star B’s lines are shifted toward the blue end. Star A's lines are also shifted a greater distance. What can astronomers conclude about the motion of each star relative to Earth, which star is moving faster and what causes these shifts?
Mr. G will show you star spectra problem
See board for answers.