1.32

1. 1
0
The light from a nearby star is
observed to be shifted toward
the blue by 2 percent; that is,
1.02 . Is the star
approaching or receding from
Earth? (How fast is it moving?
Assume motion is directly
obs
f f

toward or away from Earth so
as to avoid superluminal speeds.)
Solution

2. 2

3. 3

4. 4
Since the general expression
connecting the frequency
and wavelength λ of light is
, the shift is toward
longer wavelengths. As red is
on the longer-wavelength side
of the visible spectrum, so t
f
c f 

he
redshift is used to describe a
receding source. Similarly,
blue- shift describes light
emitted by stars that are
approaching us, typically ones
relatively nearby in our galaxy.

5. 5
Redshift and blueshift describe
the change in the frequency of
a light wave depending on
whether an object is moving
toward or away from us. When
an object is moving away from
us, the light from the object is
known as redshift, and when an
object is moving towards us, the
light from the object is known
as blueshift.

6. 6
 
In physics, a redshift is an
increase in the wavelength,
and corresponding decrease
in the frequency and photon
energy, of electromagnetic
radiation such as light .
The opposite change, a
decrease in wavelength and
simultaneous increase in
frequency and energy, is
known as a negative redshift,
or blueshift.

7. 7
0
8
8 6
Using
1 1
1.02
1 1
1
1.04
1
1.04 1.04 1 0
0.04 2.04 0 0.0196
0.0196
0.0196
0.0196 2.998 10
0.0588 10 5.88 10
obs
f
f
v
c
v c
m
X X
s
m m
X X
s s
 
 


 
 
 
  
 

 

    
    
 
 

 