The document discusses the Doppler effect and its applications in biomedical engineering. It begins with a brief history of the Doppler effect and an explanation of what it is. It then covers the physical properties of waves and the different types of waves. Next, it explains how the Doppler effect works and gives examples of its applications in areas like astronomy, radar, and ultrasound diagnostics. Doppler ultrasound is highlighted as a way to non-invasively measure blood flow and detect issues like blood clots or narrowed arteries.

1. Cairo university
Faculty of engineering
Biomedical engineering
First year
Physics report
Represented to Dr.Mohamed Hesham
Represented by: Mahmoud Helmi Ghareeb
Section ( 3 )
Application of Doppler effect in biomedical

2. History.
What is the Doppler effect ?
Physical properties of waves.
Types of waves.
Explaning the Doppler effect.
Application of Dopller effect.
Application of Doppler effect in biomedical.

3. History
Doppler first proposed this effect in 1842 in his treatise "Über das
farbige Licht der Doppelsterne und einiger anderer Gestirne des
Himmels" (On the coloured light of the binary stars and some other
stars of the heavens). The hypothesis was tested for sound waves
by Buys Ballot in 1845. He confirmed that the sound's pitch was higher
than the emitted frequency when the sound source approached him,
and lower than the emitted frequency when the sound source receded
from him. Hippolyte Fizeau discovered independently the same
phenomenon on electromagnetic waves in 1848 (in France, the effect is
sometimes called "effet Doppler-Fizeau" but that name was not adopted
by the rest of the world as Fizeau's discovery was six years after
Doppler's proposal). In Britain, John Scott Russell made an
experimental study of the Doppler effect (1848).
what is the doppler effect ?
is the change in frequency or wavelength of a wave for an observer who
is moving relative to the wave source.
The Doppler effect can be observed to occur with all types of waves water
waves, sound waves, and light waves.
To talk about the Doppler effect we need to
find out about the waves:
A wave is an oscillation accompanied by a transfer of energy. Frequency refers
to the addition of time. Wave motion transfers energy from one point to
another, which displace particles of the transmission medium–that is, with
little or no associated mass transport. Waves consist, instead, of oscillations or
vibrations (of a physical quantity), around almost fixed locations.

4. Physical properties of wave
Transmission and media
• A bounded medium if it is finite in extent, otherwise
an unbounded medium
• A linear medium if the amplitudes of different waves at any
particular point in the medium can be added
• A uniform medium or homogeneous medium if its physical
properties are unchanged at different locations in space
• An anisotropic medium if one or more of its physical properties
differ in one or more directions
• An isotropic medium if its physical properties are the same in all
directions
Absorption
When a wave strikes a reflective surface, it changes direction, such that
the angle made by the incident wave and line normal to the surface
equals the angle made by the reflected wave and the same normal line.
Interference
Waves that encounter each other combine through superposition to
create a new wave called an interference pattern. Important interference
patterns occur for waves that are inphase.
Refraction
Sinusoidal traveling plane wave entering a region of lower wave velocity
at an angle, illustrating the decrease in wavelength and change of
direction (refraction) that results.
Refraction is the phenomenon of a wave changing its speed.
Mathematically, this means that the size of the phase velocity changes.
Typically, refraction occurs when a wave passes from one medium into
another. The amount by which a wave is refracted by a material is given
by the refractive index of the material. The directions of incidence and
refraction are related to the refractive indices of the two materials
by Snell's law.

5. Diffraction
A wave exhibits diffraction when it encounters an obstacle that bends
the wave or when it spreads after emerging from an opening. Diffraction
effects are more pronounced when the size of the obstacle or opening
is comparable to the wavelength of the wave.
Polarization
The phenomenon of polarization arises when wave motion can occur
simultaneously in two orthogonal directions. Transverse waves can be
polarized, for instance. When polarization is used as a descriptor
without qualification, it usually refers to the special, simple case of linear
polarization. A transverse wave is linearly polarized if it oscillates in only
one direction or plane. In the case of linear polarization, it is often useful
to add the relative orientation of that plane, perpendicular to the
direction of travel, in which the oscillation occurs, such as "horizontal"
for instance, if the plane of polarization is parallel to the ground.
Electromagnetic propagating in free space, for instance, are transverse;
they can be polarized by the use of a polarizing filter.
Longitudinal waves, such as sound waves, do not exhibit polarization.
For these waves there is only one direction of oscillation, that is, along
the direction of travel.
Dispersion
A wave undergoes dispersion when either the phase velocity or
the group velocity depends on the wave frequency. Dispersion is most
easily seen by letting white light pass through a prism, the result of
which is to produce the spectrum of colors of the rainbow. Isaac
Newton performed experiments with light and prisms, presenting his
findings in the Optics (1704) that white light consists of several colures
and that these colures cannot be decomposed any further.

6. Types of Waves in Physics
Longitudinal waves – In this type of wave, the movement of the particle
are parallel to the motion of the energy i.e. the displacement of the medium is
in the same direction to which the wave is moving. Example – Sound Waves,
Pressure Waves.
Transverse waves – When the movement of the particles are at right angles
or perpendicular to the motion of the energy, then this type of wave is known
as Transverse wave. Light is an example of a transverse wave. Some of the
other examples are – ‘Polarized’ waves & Electromagnetic waves.
Note : Water waves are an example of combination of both
longitudinal and transverse motions.

7. Explaining the Doppler Effect
The Doppler effect is observed because the distance between the
source of sound and the observer is changing. If the source and the
observer are approaching, then the distance is decreasing and if the
source and the observer are receding, then the distance is increasing.
The source of sound always emits the same frequency. Therefore, for
the same period of time, the same number of waves must fit between
the source and the observer. if the distance is large, then the waves can
be spread apart; but if the distance is small, the waves must be
compressed into the smaller distance. For these reasons, if the source
is moving towards the observer, the observer perceives sound waves
reaching him or her at a more frequent rate (high pitch). And if the
source is moving away from the observer, the observer perceives sound
waves reaching him or her at a less frequent rate (low pitch). It is
important to note that the effect does not result because of
an actual change in the frequency of the source. The source puts out
the same frequency; the observer only perceives a different frequency
because of the relative motion between them. The Doppler effect is a
shift in the apparent or observed frequency and not a shift in the actual
frequency at which the source vibrates.

8. Application of Doppler effect :
Sirens
The siren on a passing emergency vehicle will start out higher than its
stationary pitch, slide down as it passes, and continue lower than its
stationary pitch as it recedes from the observer. Astronomer John
Dobson explained the effect thus:
"The reason the siren slides is because it doesn't hit you."
In other words, if the siren approached the observer directly, the pitch
would remain constant until the vehicle hit him, and then immediately
jump to a new lower pitch. Because the vehicle passes by the observer,
the radial velocity does not remain constant, but instead varies as a
function of the angle between his line of sight and the siren's velocity:
Vradial = Vs . cos θ
where θ is the angle between the object's forward velocity and the line of sight from the object to the observer.
Astronomy
The Doppler effect for electromagnetic waves such as light is of great use
in astronomy and results in either a so-called redshift or blueshift. It has
been used to measure the speed at which stars and galaxies are
approaching or receding from us; that is, their radial velocities. This may
be used to detect if an apparently single star is, in reality, a close binary, to
measure the rotational speed of stars and galaxies, or todetect exoplanets.
This redshift and blueshift happens on a very small scale, if an object is
moving toward earth, there would not be a noticeable difference in visible
light .
Note that redshift is also used to measure the expansion of space, but that
this is not truly a Doppler effect.Rather, redshifting due to the expansion of
space is known as cosmological redshift, which can be derived purely from
the Robertson-Walker metric under the formalism ofGeneral Relativity.
Having said this, it also happens that there are detectable Doppler effects
on cosmological scales, which, if incorrectly interpreted as cosmological in
origin, lead to the observation of redshift-space distortions.

9. The use of the Doppler effect for light in astronomy depends on our
knowledge that the spectra of stars are not homogeneous. They
exhibitabsorption lines at well defined frequencies that are correlated with
the energies required to excite electrons in various elements from one
level to another. The Doppler effect is recognizable in the fact that the
absorption lines are not always at the frequencies that are obtained from
the spectrum of a stationary light source. Since blue light has a higher
frequency than red light, the spectral lines of an approaching astronomical
light source exhibit a blueshift and those of a receding astronomical light
source exhibit a redshift.
Among the nearby stars, the largest radial velocities with respect to the Sun are +308 km/s (BD-15°4041, also known
as LHS 52, 81.7 light-years away) and -260 km/s (Woolley 9722, also known as Wolf 1106 and LHS 64, 78.2 light-
years away). Positive radial velocity means the star is receding from the Sun, negative that it is approaching.
Radar
The Doppler effect is used in some types of radar, to measure the velocity
of detected objects. A radar beam is fired at a moving target — e.g. a
motor car, as police use radar to detect speeding motorists — as it
approaches or recedes from the radar source. Each successive radar
wave has to travel farther to reach the car, before being reflected and re-
detected near the source. As each wave has to move farther, the gap
between each wave increases, increasing the wavelength. In some
situations, the radar beam is fired at the moving car as it approaches, in
which case each successive wave travels a lesser distance, decreasing
the wavelength. In either situation, calculations from the Doppler effect
accurately determine the car's velocity. Moreover, the proximity fuze,
developed during World War II, relies upon Doppler radar to detonate
explosives at the correct time, height, distance, etc.

10. Because the doppler shift affects the wave incident upon the target as
well as the wave reflected back to the radar, the change in frequency
observed by a radar due to a target moving at relative velocity ∆v is
twice that from the same target emitting a wave:
∆f=2∆vc f0
Application of Doppler effect in biomrdical :
Doppler Ultrasound
Doppler Ultrasound Diagnoses
Because Doppler is used to measure changes in sound waves, it is used to
diagnose conditions related to circulation and blood flow. The Doppler
ultrasound can actually measure how fast or slow blood is moving, which can
indicate a circulatory problem. Blood clots can be found using Doppler
ultrasound because the ultrasound will be able to detect slower blood flow or a
lack of blood flow where the clot is located. Doppler ultrasound can also be
used to identify narrowed arteries, plaque buildup in the blood vessels, or
blocked arteries. Found early, many of these conditions can be treated before
they become more serious.
Doppler Ultrasound Procedure
The Doppler ultrasound may be done on the neck or on the extremities of the
body, depending on what symptoms the patient is experiencing. This test is
performed exactly like a regular ultrasound. The technician applies gel to the
area being tested, a transducer is moved over the gelled area, and the
ultrasound machine interprets the sound waves and creates pictures of what is
happening inside the body.
Doppler Ultrasound Benefits
The main benefit of Doppler ultrasound is that it is less invasive than other
procedures used to identify these types of medical problems. The ultrasound is
perform on the outside of the body and is not painful. Some discomfort may be
experienced as the transducer is used, but it is often minimal. Because the
ultrasound is not invasive, there are fewer risks to using it as a diagnostic test
and many patients are able to have serious conditions detected without having
to spend extensive time in the hospital.