presented by crazy scientist of future

1. THE DOPPLER EFFECT FOR LIGHT
Presented by: Nahdia Nadeem

2. CONTENTS
 Definition
 Explanation
 Red shift and blue shift
 Doppler frequency
 Fractional wavelength change
 Applications

3. DEFINITION
The
Doppler
Effect for
light is the
change in
the
observed
frequency
or
wavelength
/color
compared
with that
emitted
from a
moving
source.

4. EXPLANATION
 Besides sound and radio waves, the Doppler effect
also affects the light emitted by other bodies in
space
 The Doppler effect causes the received frequency
of a source (how it is perceived when it gets to its
destination) to differ from the sent frequency if there
is motion that is increasing or decreasing the
distance between the source and the receiver
 It may be red shifted or blue shifted…..

5. BLUE SHIFT AND RED SHIFT
 Light emitted from an
object moving towards
you will have its
wavelength shortened.
 Light emitted from an
object moving towards
you will have its
frequency increased.
 Light emitted from an
object moving away
from you will have its
wavelength
lengthened.
 Light emitted from an
object moving away
from you will have its
frequency shortened.
BLUESHIFT REDSHIFT

6. BLUE SHIFT AND RED SHIFT (DIAGRAM)

7. DOPPLER FREQUENCY
Frequency equations
In the case of visible light or electromagnetic waves, the speed of light is much
greater than the typical speed of the source. In such a case, the standard
Doppler Effect equation is used.
Standard Doppler Effect equation
The equation or formula for the observed frequency of a waveform for a moving
source is:
fo = fv/(v ± vs)
where
fo is the observed frequency
v is the velocity of the waveform
vs is the velocity of the source
f is the emitted frequency
± is plus or minus; plus (+) is used when motion is away from you and minus (−)
is used when motion is toward you

8. FRACTIONAL WAVELENGTH CHANGE
A shift in frequency of electromagnetic radiation is not readily
measured. Instead, devices such as a spectroscope is used to
measure a change in wavelength of the light. Knowing the
velocity of the moving source of light (vs), you can use the
equations c = fλ and f = c/λ to convert the frequency equations
to solve for wavelength.
Blue-shift wavelength equation
The blue-shift equation for
wavelength is:
λb = λc/(c + vb)
where
λb is the observed blue-shift
wavelength
λ is the emitted wavelength
(Greek symbol lambda)
Red-shift wavelength equation
The red-shift equation for wavelength
is:
λr = λc/(c − vr)
where
λris the observed red-shift wavelength
λ is the emitted wavelength (Greek
symbol lambda)

9. APPLICATIONS
 Radar
 Medical imaging
 Blood flow measurement
 Velocity profile measurement
 Satellite communication
 astronomy

10. ANY QUESTION??????????