This document discusses topics in modern physics including blackbody radiation, Planck's constant, the photoelectric effect, Einstein's equation, lasers, and applications of lasers. It explains that blackbodies emit electromagnetic radiation depending only on temperature, and Planck calculated blackbody curves using discrete energy levels. Einstein's explanation of the photoelectric effect established that light is quantized into discrete packets called photons. Lasers produce highly coherent, monochromatic, and directional light through stimulated emission using population inversion. Common laser types and applications like welding, medicine, and communication are also outlined.

1. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
II SEMESTER
FIRST YEAR DIPLOMA IN
CME, PCT
POLYTECHNIC
THE MAHARAJA SAYAJIRAO UNIVERSITY OF BARODA
APPLIED PHYSICS-II

2. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
BLACK-BODY RADIATION
All objects with a temperature above absolute zero (0 K, -273.15 oC) emit energy in
the form of electromagnetic radiation.
A blackbody is a theoretical or model body which absorbs all
radiation falling on it, reflecting or transmitting none. It is a
hypothetical object which is a “perfect” absorber and a “perfect”
emitter of radiation over all wavelengths.
The spectral distribution of the thermal energy radiated
by a blackbody depends only on its temperature.
Figure illustrates how the intensity per unit
wavelength depends on wavelength for a perfect
blackbody emitter.
At the higher temperature, the intensity per unit
wavelength is greater, and the maximum occurs
at a shorter wavelength.

3. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
PLANCK'S CONSTANT
• In 1900 Planck calculated the blackbody radiation curves and represents
blackbody as a large number of atomic oscillators, each of which emits and
absorbs electromagnetic waves.
• Planck assumed that the energy E of an atomic oscillator could have only the
discrete values of E=0, hf, 2hf, 3hf, and so on. In other words, he assumed that
𝐸 = 𝑛ℎ𝑓 𝑛 = 0,1,2,3, ⋯ −− −(1)
where n is either zero or a positive integer, f is the frequency of vibration (in hertz),
and h is a constant now called Planck’s constant. Experimentally that Planck’s
constant has a value of
ℎ = 6.626 × 10−34
𝐽 ∙ 𝑠
• For conservation of energy, the energy carried off by the radiated electromagnetic
waves must equal the energy lost by the atomic oscillators in Planck’s model.
• The energy carried off by the electromagnetic wave = The energy lost by the
oscillator = hf.
• According to Planck’s model the electromagnetic energy occurs as a collection of
discrete amounts, or packets, of energy, with the energy of a packet being equal
to hf.

4. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
PHOTOELECTRIC EFFECT
Visible light and all other types of electromagnetic waves are composed of discrete
particle-like entities called photons.
The electrons are emitted from a metal surface when
illuminated by light or any other radiation of suitable
frequency or wavelength called the photoelectric
effect.
The electrons are emitted if the light being used has
a sufficiently high frequency. The ejected electrons
move toward a positive electrode (anode) called the
collector. Because the electrons are ejected with the
aid of light, they are called photoelectrons.
The current, set up due to photoelectrons, is called
the photoelectric current.
Figure illustrates the photoelectric effect, light with
a sufficiently high frequency ejects electrons from a
metal surface.

5. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
EINSTEIN’S EQUATION
In 1905 Einstein presented an explanation of the photoelectric effect. Einstein was
awarded the Nobel Prize in physics in 1921 for his theory of the photoelectric effect.
According to Einstein, when a metal illuminated by light, a photon can give up its
energy to an electron in the metal. If the photon has enough energy to do the work
of removing the electron from the metal, the electron can be ejected.
The minimum work (W0= hf0 ) needed to ejected the electron from metal is called
the work function of the metal. If a photon has energy in excess of the work
needed to remove an electron, the excess energy appears as kinetic energy of the
ejected electron. Einstein proposed the following relation to describe the
photoelectric effect: ด
ℎ𝑓
𝑃ℎ𝑜𝑡𝑜𝑛
𝑒𝑛𝑒𝑟𝑔𝑦
= 𝐾𝐸𝑚𝑎𝑥
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑘𝑖𝑛𝑒𝑡𝑖𝑐 𝑒𝑛𝑒𝑟𝑔𝑦
𝑜𝑓 𝑒𝑗𝑒𝑐𝑡𝑒𝑑 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛
+ ด
𝑊0
𝑀𝑖𝑛𝑖𝑚𝑢𝑚 𝑤𝑜𝑟𝑘 𝑛𝑒𝑒𝑑𝑒𝑑
𝑡𝑜 𝑒𝑗𝑒𝑐𝑡 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛
𝐸 = ℎ𝑓 where h is Planck’s constant.
Energy of a photon
Einstein proposed that light of frequency f could be regarded as a collection of
discrete packets of energy (photons), each packet containing an amount of energy
E given by
∴ 𝐾𝐸𝑚𝑎𝑥
1
2
𝑚𝑣2
= ℎ𝑓 − ℎ𝑓0 = ℎ𝑐
1
𝜆
−
1
𝜆0
Einstein’s photoelectric
equation

6. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
EINSTEIN’S EQUATION ……Cont…
• It is observed, for instance, that only light with a frequency above a certain
minimum value f0 will eject electrons. If the frequency is below this value, no
electrons are ejected, regardless of how intense the light is.
• Another significant feature of the photoelectric effect is that the maximum
kinetic energy of the ejected electrons remains the same when the intensity of
the light increases, provided the light frequency remains the same.
• As the light intensity increases, more photons per second strike the metal, and
consequently more electrons per second are ejected. However, since the
frequency is the same for each photon, the energy of each photon is also the
same. Thus, the ejected electrons always have the same maximum kinetic
energy.
Threshold frequency (f0):
It is the minimum frequency of the incident radiation which can cause the photo-
electric emission.
Electron Volt (eV):
The electron volt is the unit of energy. It is the energy acquired by an electron
when it moves through a potential difference of 1 volt. 1 eV = 1.6 × 10-19 joule.

7. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
APPLICATION OF PHOTOELECTRIC EFFECT
The photoelectric effect has many practical applications which include the photocell,
photoconductive devices and solar cells.
Automatic Doors
Many elevators and garage-door systems use a beam of light and a photoelectric
device known as a photocell as a safety feature. As long as the beam of light
strikes the photocell, the photoelectric effect generates enough ejected electrons to
produce a detectable electric current. When the light beam is blocked (by a
person) the electric current is interrupted and the doors are signaled to open.
Solar Energy Panels
Photocells are also the basic unit in the solar energy panels that convert some of
the energy in sunlight into electrical energy. These panels are able to operate
billboards and safety lights in remote areas far from power lines.
Others application of a Photocell and Solar Energy
• Television Camera Tubes
• Light-Activated Counters
• Automatic Doors
• Intrusion Alarms
• Turn on Street Lights at Dawn
• Pocket Calculators
• Turn on Safety Lights

8. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
X-RAYS
In an X-ray tube, electrons are
emitted by a heated filament,
accelerate through a large potential
difference V, and strike a metal
target. The X-rays originate when
the electrons interact with the target.
X-rays were discovered by the Dutch physicist Wilhelm K. Roentgen. X-rays can
be produced when electrons, accelerated through a large potential difference,
collide with a metal target made, for example, from molybdenum or platinum. The
target is contained within an evacuated glass tube, as Figure shows.
X-rays make up X-radiation, a form of electromagnetic radiation. Most X-rays have
a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in
the range 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the
range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and
typically longer than those of gamma rays.

9. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
• X-rays can penetrate light materials like wood, paper, flesh, etc. which are
opaque to ordinary visible light.
• X-rays cannot penetrate through heavy metals and bones and cast the shadow
of these objects when placed in their path.
• X-rays blackening on photographic plates when they are incident on them.
• X-rays are electromagnetic waves of very short wavelength ranging from 1 to
100 angstrom unit and travel in straight lines with a velocity of light.
• Wavelengths of X-rays are shorter than those of ultraviolet rays and typically
longer than those of gamma rays.
• X-rays produce ionization in a gas through which they pass.
• When X-rays are incident on a fluorescent substance like zinc sulphide, the
substance is excited to fluorescence.
• When X-rays fall on heavy metals, they produce secondary X-rays.
• X-rays are not deflected by electric and magnetic field.
• X-rays cannot be reflected by ordinary mirrors or refracted by lenses and
prism. They exhibit diffraction by crystals.
Some Properties of X-rays
X-RAYS

10. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
• In industry: X-rays are used to detect faults, cracks, flaws and gas bubbles in
finished metal products. They are used to test weldings, castings, moulds,
uniformity of an insulating substance.
• In scientific research: X-rays are used to study and analyzed the structure of
atoms, crystalline solids, organic compounds, composite bodies, alloys and
arrangement of atoms and molecule in complex substances.
• In detective departments: X-rays are used for detection of explosive and
contraband goods is sealed parcels.
• In the medical profession: X-rays photography called radiographs, are used to
detect fractures of bones, tuberculosis of lungs, foreign matter like bullets, the
formation of bones and stones in the body.
X-rays are used in treating cancer when surgery is not permissible. Cancer tissue
is exposed to X-rays for a few minutes every day till it is completely destroyed.
X-rays are used to destroy abnormal tissues and tumors deep inside the body.
Some Uses or Applications of X-rays
X-RAYS

11. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
APPLICATIONS X-RAYS

12. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
Consider an isolated atom that can exist either in its state of lowest energy E0 (ground
state), or in a state of higher energy Ex (excited state). Here are three processes by
which the atom can move from one of these states to the other:
Absorption: The atom absorb an
amount of energy hf from electro-
magnetic field at frequency f and
move to the higher-energy state.
Spontaneous emission: The atom is
in its excited state, After a time, the
atom will de-excite to its ground state,
emitting a photon of energy hf in the
process.
Stimulated emission: A photon of
energy hf can stimulate the atom to
move to its ground state, during which
process the atom emits an additional
photon, whose energy is also hf.
Stimulated emission for a single atom
UNIT-IV MODERN PHYSICS
LASER (Light Amplification by Stimulated Emission of Radiation)

13. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
LASER (Light Amplification by Stimulated Emission of Radiation)
Although stimulated emission plays a pivotal role in a laser, other factors are also
important. If sufficient energy is delivered to the atoms, more electrons will be
excited to a higher energy level than remain in a lower level, a condition known as
a population inversion.
The population inversions used in lasers involve a
higher energy state that is metastable, in the sense
that electrons remain in the metastable state for a
much longer period of time than they do in an
ordinary excited state.
Optical pumping is a process in which light is
used to raise (pump) electrons from lower energy
level in an atom or molecule to a higher one.
Laser light has the following characteristics:
• Highly monochromatic: contains one specific wavelength of light
• Highly coherent: “organized” - each photon moves in step with the others.
• Highly directional: laser beams are very narrow and do not spread very much.
• Laser light can be sharply focused:

14. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
TYPES OF LASER
There are many different types of laser, depending on the type and whether the laser
operates continuously or in pulses, the available beam power ranges from milliwatts
to megawatts.:
• The helium/neon laser
• The ruby laser,
• The argon-ion laser,
• The carbon dioxide laser,
• The gallium arsenide solid-state laser, and
• The chemical dye lasers.
A schematic drawing of a helium/neon
laser. The blow-up shows the stimulated
emission that occurs when an electron in
a neon atom is induced to change from a
higher to a lower energy level.

15. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
• Medical Uses of Lasers: Higher power lasers are used after cataract surgery. In the
treatment of cancer, the laser is being used along with light-activated drugs in
photodynamic therapy.
• Welding and Cutting: The automobile industry makes extensive use of carbon
dioxide laser for computer controlled welding on auto assembly lines.
• Surveying and Ranging: lasers have become standard parts of the field surveyor's
equipment. A fast laser pulse is sent to a corner reflector at the point to be measured
and the time of reflection is measured to get the distance.
• Lasers in the Garment Industry: Computer controlled laser garment cutters can
be programmed to cut out garments and that might involve just a few cuts.
• Heat Treatment: For selective heat treatments to metal for hardening or annealing.
• Barcode Scanners: lasers to scan the universal barcodes to identify products.
• Lasers in Communication: The lasers allows the pulse shape to be maintained
better over long distances.
• Lasers are also used to reproduce music in compact disc players and to study
molecular structure.
SOME APPLICATIONS OF LASER
Since lasers provide coherent monochromatic electromagnetic radiation that can be
confined to an intense narrow beam, they are useful in a wide variety of situations.

16. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
To correct for myopia (nearsightedness)
using the PRK procedure, a laser vaporizes
tissue (dashed line) on the center of the
cornea, thereby flattening it.
To correct for myopia using the LASIK
technique, a laser vaporizes tissue (dashed
line) on the cornea, thereby flattening it.
To correct for hyperopia
(farsightedness), a laser
vaporizes tissue on the
peripheral region of the cornea,
thereby steepening its contour.
SOME APPLICATIONS OF LASER

17. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
• Figure shows that an optical fiber consists of a cylindrical inner core that
carries the light and an outer concentric shell, the cladding.
• The core is made from transparent glass or plastic that has a relatively high
index of refraction. The cladding is also made of glass, but of a type that has a
relatively low index of refraction.
• The outermost protective jacket, made of plastic or polymer to protects the
optical fiber from mechanical shocks and other environmental hazards.
• Light enters one end of the core, strikes the core/cladding interface at an angle
of incidence greater than the critical angle, and, therefore, is reflected back into
the core. Light thus travels inside the optical fiber along a zigzag path.
• In a well-designed fiber, little light is lost as a result of absorption by the core,
so light can travel many kilometers before its intensity diminishes appreciably.
OPTICAL FIBER

18. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
TYPES OF OPTICAL FIBERS
The properties of data transmission via a fiber optic depend on the core. Hence,
based on the differences in the structure of the core, there are two basic types of
fiber: multimode fiber and single-mode fiber.
• Multimode fiber is best designed for short transmission distances, and is suited
for use in LAN systems and video surveillance.
• Single-mode fiber is best designed for longer transmission distances, making it
suitable for long-distance telephone and multichannel television broadcast
systems.
• These types of optical fibers having a thicker core diameter and allow multiple
modes of light to travel along their axis. The wavelengths of light waves in
multimode fibers are in the visible spectrum ranging from 850 to 1300 nm.
• The reflection of the waves inside the multimode fiber occurs at different angles
for every mode.
• Since the basis of optical fiber communication is a total internal reflection, all
modes with incident angles that do not cause total internal reflection get absorbed
by the cladding. As a result, losses are created.
Multimode optical fiber
OPTICAL FIBER

19. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
There are two types of multimode optical fibers: stepped index and graded index.
Cont……..Multimode optical fiber
• Stepped index multimode fiber : The refractive index of the core of the
multimode is uniform throughout the cable. Because the core's index of refraction
is higher than the cladding's index of refraction, the light that enters at less than
the critical angle is guided along the fiber.
• Graded-index multimode fiber : The refractive index of the core changes
radially from the center of the core to its surface. The refractive index of the core
gradually decreases from the center of the core to its surface. The core's central
refractive index n1 is greater than that of the outer core's refractive index n2. The
core's refractive index is parabolic, being higher at the center.
OPTICAL FIBER

20. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
• Single-mode fiber is a step-index fiber meaning the refractive index of the
fiber core is a step above that of the cladding.
• The diameter of the core is essentially of the same order as the wavelength of
the light passing through it. It can carry only one wavelength of light across
its length. This wavelength is usually 1310 nm or 1550 nm.
• The single mode type of optical fibers is much better than multimode optical
fibers as they have more bandwidth and experience fewer losses.
• Single mode fibers came into existence after multimode fibers. They are more
recent than the multimode cables.
• Only lasers are used as a light source. The light used in single mode fibers are
not in the visible spectrum.
• Since the light travels in a straight direction, there are fewer losses, and it can
be used in applications requiring longer distance connections.
• An obvious disadvantage of single mode fiber is that they are hard to couple.
Single mode or Mono-mode optical fiber
TYPES OF OPTICAL FIBERS OPTICAL FIBER

21. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
Advantage of Optical fibre:
• Optical fibers are light in weight and occupy less space than coaxial cables.
• They are made of dielectric materials (i.e. silica) which are easily available
in nature.
• There is virtually no signal leakage so cross talks between neighboring are
not possible.
• Optical fibers do not mix up with other communication systems as they are
non-conductive and non-inductive.
• It covers large range of frequency band to propagate in the medium with very
little loss of signals.
• The attenuation (loss of signals) of signals is much smaller than in twisted
pair cable.
OPTICAL FIBER

22. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
APPLICATIONS
• Communication: Optical fibres are used to carry signals in optical
communications without any loss of signal in transmission of speech, video
or digital data. It may replace the existing copper based electrical lines used
for communication.
• Scanning: Optical fibres can be used to measure the distribution of light
intensity over the scanned area.
• Medical instruments: It is used to examine the internal body cavities such
as stomach and bladder. It is also used to study tissues and blood vessels
which are below the skin.
• Computers: It can be used for interfacing of central processor with other
peripheral devices and data transmission within the main frame.
• LAN: Fibres are used to link computers in ring, star or bus networks.
• Industrial electronics: They are used in power plants, rail road networks
and metal industry for data acquisition control and signal processing.
• Display and Illumination: They are used to carry light to the display units.
They are also used to illuminate dials when measuring instruments are used
in dim light.
OPTICAL FIBER

23. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
SOME APPLICATIONS
• Communication: (Internet, Cable Television, Telephone, Computer Networking):
Fiber optic cables transmit large amounts of data at very high speeds, therefore
widely used in internet cables, for transmitting signals for high definition
televisions, one can connect faster and have clear conversations without any lag on
either side of telephone. Networking between computers in a single building or
across nearby structures is made easier and faster with the use of fiber optic cables.
• Surgery and Dentistry: Fiber optic cables are widely used in the fields of
medicine and research. Optical communication is an important part of non-
intrusive surgical methods, popularly known as endoscopy. Fiber optics are also
used in microscopy and biomedical research.
• Mechanical Inspections: Fiber optic cables are widely used in the inspection of
hard-to-reach places.
• Military and Space Applications: With the high level of data security required in
military and aerospace applications, fiber optic cables offer the ideal solution for
data transmission in these areas.
• Automotive Industry: Fiber optic cables play an important role in the lighting and
safety features of present day automobiles. They are widely used in safety
applications such as traction control and airbags.
OPTICAL FIBER

24. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
There is a class of metals and compounds whose resistance decreases to zero when
they are below a certain temperature Tc, known as the critical temperature. These
materials are known as superconductors.
• The R()–T(K) graph for a superconductor follows that of a
normal metal at temperatures above Tc . When the temperature
is at or below Tc, the resistivity drops suddenly to zero.
• This phenomenon was discovered in 1911 by the physicist
Heike Kamerlingh-Onnes as he worked with mercury, which is
a superconductor below 4.2 K.
• The value of Tc is sensitive to chemical composition, pressure,
and molecular structure. It is interesting to note that copper,
silver, and gold, which are excellent conductors, do not exhibit
superconductivity.
The superconducting material shows some extraordinary properties which make
them very important for modern technology. The research is still going on to
understand and utilize these extraordinary properties of superconductors in various
fields of technology.
SUPERCONDUCTORS

25. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
MEISSNER EFFECT
High-speed trains have been developed that levitate on strong superconducting
magnets, eliminating the friction normally experienced between the train and the
tracks.
In April 2015, the MLX01 test vehicle attained a speed of 374 mph (603 km/h).
• Certain types of superconductors also exhibit perfect
diamagnetism in the superconducting state. As a result, an
applied magnetic field is expelled by the superconductor
so that the field is zero in its interior. This phenomenon is
known as the Meissner effect.
SUPERCONDUCTORS
• If a permanent magnet is brought near a superconductor,
the two objects repel each other. This is illustrated in
Figure, which shows a small permanent magnet levitated
above a superconductor maintained at 77 K.
• A small, strong magnet levitates over a superconductor
cooled to liquid nitrogen temperature. The magnet
levitates because the superconductor excludes magnetic
fields.

26. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
Type I Superconductors
Superconductor materials offer no resistance to electric current and are, therefore,
perfect conductors. Superconductors have many applications, including magnetic
resonance imaging, magnetic levitation of trains, cheaper transmission of electric
power, powerful (yet small) electric motors, and faster computer chips.
Superconductors come in two different flavors: type I and type II.
• A type I superconductor consists of basic conductive elements that are used in
everything from electrical wiring to computer microchips.
• At present, type I superconductors have Tcs between 0.000325°K and 7.8°K
at standard pressure.
• Some type I superconductors require incredible amounts of pressure in order
to reach the superconductive state. One such material is sulfur which, requires
a pressure of 9.3 million atmospheres (9.4 x 1011 N/m2) and a temperature of
17°K to reach superconductivity.
• Some other examples of type I superconductors include Mercury - 4.15°K,
Lead - 7.2°K, Aluminum - 1.175°K and Zinc - 0.85°K. Roughly half of the
elements in the periodic table are known to be superconductive.
SUPERCONDUCTORS

27. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
Type II Superconductors
• A type II superconductor is composed of metallic compounds such as copper or
lead. They reach a superconductive state at much higher temperatures when
compared to type I superconductors.
• The highest Tc reached at stardard pressure, to date, is 135°K or -138°C by a
compound (HgBa2Ca2Cu3O8) that falls into a group of superconductors known as
cuprate perovskites.
• This group of superconductors generally has a ratio of 2 copper atoms to 3 oxygen
atoms, and is considered to be a ceramic.
• Type II superconductors can also be penetrated by a magnetic field where as a
type I can not.
SUPERCONDUCTORS

28. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-III MODERN PHYSICS
SUPERCONDUCTORS

29. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University
UNIT-IV MODERN PHYSICS
SOME APPLICATION
• The strongest man made permanent magnetic fields are produced using
superconductors. Superconducting magnets are used in MRI (Magentic
Resonance Imaging) which is a way of looking at the soft parts of the body.
• They are also going to be used in the new ‘Large Hadron Collider’ experiment at
the CERN Particle Physics Lab. The idea is to accelerate protons and antiprotons
to almost the speed of light in a circle and then smash them together. To keep the
particles in a circle requires huge magnetic fields which can only be provided by
superconductors.
• It is also possible to use superconducting magnets to produce a levitating train.
The idea is to put very powerful light superconducting magnets on the train, then
use copper coils in the track which use repulsion to lift the train up to make it
levitate. It is also possible to use the track magnets to push the train along.
• Due to a subtlety of the quantum mechanics of how superconductors interact with
magnetic fields, it is possible to make the most sensitive magnetometers possible
called SQUIDs (Superconducting Quantum Interference Devices). These can be
used to detect submarines, measure the magnetic field produced by your brain,
find ore deposits deep underground, sense minute signals from stars etc.
SUPERCONDUCTORS

30. Dr.
Virendrasinh
Kher
Applied
Physics
Dept.,
Polytechnic,
The
M.
S.
University