Name: ____________________________________
Period: ____
Key Points on The Doppler Effect and Astronomy:
1. If a moving object is producing waves (electromagnetic or sound), the wavelengths of
these waves will be changed by the object’s motion.
a. If an object is moving toward the observer, the waves will be compressed
(pushed together) and the wavelength will decrease.
1) For a sound wave, this will cause a higher pitched sound.
2) For EM waves, this will cause the color to shift toward the blue
end of the electromagnetic spectrum. This is called blue shift.
b. If an object is moving away from the observer, the waves will spread
apart and the wavelength will increase.
1) For a sound wave, this will cause a lower pitched sound.
2) For EM waves, this will cause the color to shift toward the red end
of the electromagnetic spectrum. This is called red shift.
c. This is called the Doppler Effect.
2. The Doppler Effect gives astronomers many new tools for studying the
universe.
a. Scientists can determine if a star or galaxy is moving toward us or away from us
and how fast it is doing so by studying the red or blue shift of the object.
b. Scientists have determined that the universe is expanding because the oldest
stars are exhibiting red shift.
The Doppler Effect and Astronomy: Guided Practice
Fill in the blanks in the table below using the given information.
#1
#2
#3
#4
Predicted
Green
Blue
UV Light
Infrared
Observed
Orange
Infrared
X-Ray
Microwave
Type of Shift
Red
Red
Blue
Red
#5
Radio
Infrared
Blue
#6
Green
UV Light
Blue
The Doppler Effect and Astronomy: Independent Practice
Answer the following questions as a scientist would, using COMPLETE sentences! You may
use the table showing wavelengths of visible light to help you.
1. If an object moves away from an observer, what will occur to
light waves it produces?
2. If the light produced by the object is at 450 nm, what color is
being produced by the object?
Color
violet
blue
green
yellow
orange
red
3. Give an estimate for the wavelength of light received by the observer.
Wavelength
380–450 nm
450–475 nm
495–570 nm
570–590 nm
590–620 nm
620–750 nm
Name: ____________________________________
Period: ____
4. What is the name for the phenomenon described in #1?
5. If an object moves toward an observer, what will occur to sound waves it produces?
6. What is the name for the phenomenon described in #4?
7. A sample of laser light is undergoing red shift. If it has a wavelength of 570 nm when it
leaves the laser, what color will the light be when it impacts the observer?
8. The sun produces yellow light at a wavelength of 570 nm. If the sun is moving toward
Alpha Centauri, what is a possible color and wavelength of the light when it reaches
Alpha Centauri?
9. For an object to produce the Doppler Effect, what must be true about it?