QUE 1 >
A> Define electric field intensity, Polarisation, electric susceptibility and Dielectric constant and Derive the mathematical relation among them.
ANS> Electric field intensity: It is defined as the force per unit charge that is exerted
on a test charge.
Polarization: Polarization it is defined as the induced dipole moment per
unit volume of the dielectric
Electric Susceptibility: A measure of how easily a material can become polarized when subjected to an electric field, represented by the symbol χ (chi).
Dielectric constant: It is defined as the ratio between the permittivity of medium and the permittivity of free space.
B>
Define Magnetisation, Permeability and Explain the Hysteresis curve
along with neat and clean diagram.
Magnetization: It is the measure of the magnetic moment per unit volume of a material. When a material is placed in an external magnetic field, the alignment of its atomic or molecular magnetic dipoles results in magnetization.
Permeability is a property of a material that describes its ability to support the formation of a magnetic field within it when subjected to an external magnetic field. It quantifies how easily magnetic lines of flux can pass through a material. Permeability is denoted by the symbol μ (mu)
Hysteresis Curve: A hysteresis curve, also known as a magnetic hysteresis loop, is a graphical representation of the relationship between the magnetic field strength (H) and the magnetic flux density (B) in a magnetic material. It illustrates the behavior of the material when the magnetic field is increased and then decreased.
The hysteresis curve demonstrates the phenomenon of hysteresis, which is the lagging of the magnetic response of a material behind the magnetic field. The curve shows the magnetization process as the magnetic field strength is increased from zero to its maximum value (positive saturation), and then gradually reduced back to zero (negative saturation), while measuring the corresponding magnetic flux density.
The hysteresis loop diagram typically consists of a closed loop, indicating that there is a residual magnetization remaining even when the magnetic field is removed. The area enclosed by the loop represents the energy loss (hysteresis loss) in the material during a complete cycle of magnetization and demagnetization.
QUE 2>
A>
Define the terms: (i) Pitch (ii) Intensity level (i) Acoustic (iii) Loudness (iv) SONAR (v) Piezo electric effect
(i) Pitch: Pitch refers to the perceived frequency of a sound, determining whether it is high or low.
(ii) Intensity level (Acoustic): Intensity level measures the power or energy carried by a sound wave per unit area, quantifying the loudness or strength of a sound.
(iii) Loudness: Loudness refers to the subjective perception of the intensity or volume of a sound.
(iv) SONAR: SONAR (Sound Navigation And Ranging) is a system that uses sound waves to detect and locate objects underwater.
(v) Piezoelectric Effect: Piezoelectric effect is the generation of an electric charge in certain materials when subjected to mechanical stress or pressure, and vice versa.
B>
Discuss the various properties of superconductors along with necessary diagram/formula.
Superconductors possess unique properties:
- Zero Electrical Resistance: They exhibit no resistance, allowing for efficient electrical current flow.
- Critical Temperature (Tc): Below this temperature, superconductivity is observed.
- Meissner Effect: Superconductors expel magnetic fields, exhibiting perfect diamagnetism.
- Critical Magnetic Field (Hc): Above this field strength, superconductivity is suppressed.
- Persistent Currents: Superconductors can sustain a current indefinitely.
- Type I and Type II Superconductors: Type I fully expel magnetic fields, while Type II allows partial penetration.
- Cooper Pairs: Superconductivity is explained by the formation of Cooper pairs, resulting in zero electrical resistance.
QUE 3>
A>
[i]
(1) Discuss the black body and black body radiation
A black body is an idealized object that absorbs all incident electromagnetic radiation across a wide range of frequencies and does not reflect or transmit any radiation. Due to its perfect absorption, a black body also emits radiation at all wavelengths, making it an essential concept in understanding thermal radiation.
Black body radiation refers to the electromagnetic radiation emitted by a black body. The radiation is characterized by a continuous spectrum of wavelengths, known as the black body spectrum or Planck’s law. The spectrum depends solely on the temperature of the black body.
Key features of black body radiation are:
- Planck’s Law: The intensity of radiation emitted by a black body at a given wavelength is described by Planck’s law, which states that the energy density of the radiation is proportional to the temperature of the black body and follows a specific mathematical distribution.
- Wien’s Displacement Law: The peak wavelength of the black body radiation spectrum shifts inversely with temperature. Higher temperatures result in shorter peak wavelengths, shifting the spectrum toward higher frequencies (bluer light).
- Stefan-Boltzmann Law: The total power radiated by a black body is proportional to the fourth power of its absolute temperature. It quantifies the total energy emitted per unit area over all wavelengths.
Black body radiation has important applications in various fields, including astrophysics, engineering, and the study of thermal radiation. Understanding black body radiation is crucial for concepts such as thermal equilibrium, radiation heat transfer, and the behavior of stars and galaxies.
[ii]
QUE 1>Define electric field intensity, Polarisation, electric susceptibility and Dielectric constant and Derive the mathematical relation among them.
ANS>1. Electric Field Intensity : – The electric field intensity at a point is the force per unit charge.
E = F/q
Polarization : –Polarization is defined as induced surface charge per unit area.OR It is defined as dipole moment per unit volume of dielectric. P=N.µ
Electric Susceptibility : –It is a measure of a materials ability to become polarized in electric field.χe = P/ϵ0E.
Dielectric Constant : –Dielectric constant (ϵr) is defined as the ratio of the electric permittivity of the material to the electric permittivity of free space (i.e., vacuum).Its value can be derived from a simplified capacitor model.ϵr=ϵ/ϵ0.
QUE 2>Define Magnetisation, Permeability and Explain the Hysteresis curve along with neat and clean diagram.
ANS>Magnetization : –Magnetization refers to the alignment of a magnetic dipole moments in a material when external magnetic field is applied.
Permeability : -It is defined as the ratio of the magnetic induction ‘B’ to the applied field ‘H’. OR It is the ratio of magnetic field density to magnetic field intensity. Permeability is a measure of material’s ability to support the formation of magnetic field.µ=B/H
Distances is the lagging of magnetic induction ‘B’ in ferromagnetic material, which respect to applied magnetic field.
When magnetic field ‘H’ is increased from zero ‘0’ value in the positive direction shown along OH, the value of ‘B’ also increases, and the curve increases to OP.
After point P, ‘B’ remains constant inspite of the increase in ‘H’.
The value of ‘B’ at point P is known as Saturation Value.
Now when the value of ‘H’ decreases, ‘B’ starts from point P, facts to retrace the same path when it was increasing.
The new path is ‘PQ’
When H becomes zero, the value of B remains a value equal to OQ.
This residual value of magnetization is called laminae magnetization OR Retentivity.
When the value of applied magnetic field ‘H’ is reversed and increases gradually in point r, B becomes zero at point R.
Now, the material is completely demagnetized, this value of ‘H’=OR is called Coercivity.
Further increase in H causes the material to get magnetized in the opposite direction.
The curve traces to ST.
The variation of B with respect to ‘H’ along a close path gives one full cycle of magnetization and demagnetization and is called Hysterics loop OR curve.
Hysterics loss: – The energy loss in the form of heat that occurs during the full cycle of magnetization and demagnetization in a ferromagnetic material is called hysterics loss.
QUE 3>Define the terms: (i) Pitch (ii) Intensity level (i) Acoustic (iii) Loudness (iv) SONAR (v) Piezo electric effect
ANS> Pitch: Pitch is the subjective perception of a sound’s frequency, determining its highness or lowness, and is measured in hertz.
Intensity level: Intensity level is a measure of the loudness of sound waves, expressed in decibels, that compares the sound wave intensity to a reference level.
Acoustics: Acoustic is the science of sound which deals with the properties of sound waves, their origin, propagation and their action on obstacles.
Loudness: The uniform distribution of loudness in a hall or a room is an important factor for satisfactory hearing. Sometimes, the loudness may get reduced due to excess of sound-absorbing materials used inside a hall or room.
SONAR: SONAR stands for Sound Navigation and Ranging. It is a technology that uses sound waves to detect and locate objects underwater.
Piezoelectric effect: When pressure is applied to one pair of opposite faces of crystals like quartz, tourmaline, Rochelle salt, etc. cut with their faces perpendicular to its optic axis, equal and opposite charges appear across its other face. This phenomenon is known as Piezoelectric effect.
QUE 4>Discuss the various properties of superconductors along with necessary diagram/formula.
ANS>(i)Electrical resistance : The electrical resistance of a superconducting material is very low and is of the order of 10-7 Ω m.
(ii) Effect of impurities : When impurities are added to superconducting elements, the superconducting property is not lost, but the T value is lowered.
(iii) Effect of pressure and stress : Certain materials are found to exhibit the superconductivity phenomena on increasing over them. For example, cesium is found to exhibit superconductivity phenomena at Tc = 1.5K on the pressure applying a pressure of 110 Kbar. In superconductors, the increase in stress results in increase of the Tc value.
(iv) Isotope effects : The critical or transition temperature Tc value of a superconductor is found to vary with its isotopic mass. This variation in Tc ,with its isotopic mass is called the isotopic effect.
The relation between Tc , and the isotopic mass is given by
Tc∝1√M
i.e., the transition temperature is inversely proportional to the square root of the isotopic mass of a single superconductor.
(v) Magnetic field effect : If a sufficiently strong magnetic field is applied to a superconductor at any temperature below its critical temperature Tc , the superconductor is found to undergo a transition from the superconducting State to the normal state.
This minimum magnetic field required to destroy the superconducting state is called theCritical magnetic field Hc. The critical magnetic field of a superconductor is a function of temperature. The variation of Hc with temperature is given by
Hc=Ho[1−(TTc)2]———−(1)
Where Ho , is the critical field at T = 0k. The critical field decreases with increasing temperature and coming zero at T = Tc .
Figure 5.2 shows the variation of critical field Hc as a function of temperature. The material is aid to be in the superconducting state within the curve and is non-superconducting in the region outside the curve.
Critical current density Jc and critical current Ic .
QUE 5>1) Discuss the black body and black body radiation (ii) Differentiate Intrinsic and Extrinsic semiconductors
ANS> Black body: A perfect black body is one, which absorbs radiation of all wavelength’s incident upon it.
The term comes from the fact that a cold blackbody appears visually black. The black body is a composed of atoms and molecules which can emit and absorb light.
As the radiating power of a body is proportional to its absorbing power, a black body would also radiate more strongly at any given temperature than any other surface. They emit light because they are wiggling around due to their heat content (thermal energy). So a blackbody emits a certain spectrum of light that depends only on its temperature. The higher the temperature, the more light energy is emitted and the higher the frequency (shorter the wavelength) of the peak of the spectrum. The radiations emitted from the black body are independent of the nature of the body.
QUE 6>Derive an expression for Schrodinger time independent and time dependent wave equations.
ANS>
QUE 7>Define Diffraction. Explain the types of diffraction phenomena of light with example.
ANS>The bending of waves around an obstacle and deviation from a rectilinear path is called Diffraction.
It is matter matter of common experience that the path of light entering a dark room through hole in the window illuminated a by sunlight is straight But it has been observed that when a beam of light passes through a small opening it spreads to some extent into the region of the geometrical shadow also.
When Waves pass near an obstacle (barrier), they bend to bend around the edges of the obstacle.
The diffraction are divided into two classes, (i) Fresnel diffraction (ii) Fraunhofer diffraction
Fresnel diffraction: In this class of diffraction, the source of light and the screen are at finite distance from the diffracting aperture or obstacle having sharp edge. The wave front incident on the aperture or obstacle is either spherical or cylindrical.
Fraunhofer diffraction: In this class of diffraction the source of light and the screen are at finite distance from the diffraction aperture or obstacle having sharp edge. This can be achieved by placing the light source at the focal plane of the convex lens and placing the screen at the focal plane of another convex lens. In this case the wave front incident on the aperture or obstacle is a plane wave front.
QUE 8>Describe the construction and working principle of Nd:YAG laser along with necessary diagram.
ANS>Construction:
Nd-YAG Laser This laser system has two absorption bands (0.73 m and 0.8 m)
Optical pumping mechanism is employed.
Laser transition takes place between two laser levels at 1.06 mm.
A Nd: YAG rod and a krypton flash lamp are enclosed inside an ellipsoidal reflector. In order to make the entire flash radiation to focus on the laser rod, the Nd: YAG rod is placed at one focal axis and the flash lamp at the other focal axis of the ellipsoidal reflector.
Working:
Energy level Diagram The flash lamp is switched on. The optical pumping excites the Nd3+ ions from the ground energy state E0 to the higher energy level E3 and E4 by absorbing radiations of wavelength 0.80 μm and 0.73 pm, respectively. The energy-level diagram is shown in Figure 6.5. The excited Nd3+ ions then make a transition from these energy levels. The transition from the energy level E4 to E2 is a non-radiative transition. The state E2 is the metastable state. Upon continuous excitation, population inversion of Nd3+ ions is achieved at the metastable state E2.
Any of the spontaneously emitted photon will make the excited Nd3+ ions to undergo a transition between E2→E1 state. Thus, during this transition the stimulated photon is generated. The photons travelling parallel to the resonator axis experience multiple reflections at the mirrors. As a result, the transition E2→E1 yields an intense and coherent laser beam of wavelength 1.064 um. These lasers give beam continuously. The Nd3+ ions then make a transition between E1→E0 which is a non-radiative transition
QUE 9>What do you mean by Photon? Calculate the energy in eV for a photon of wavelength 0.1x10m. What is the momentum of this photon.
ANS> Photon, also known as light quantum, is a minute energy packet of electromagnetic radiation
λ = 0.1×10-9 m, E = ?, p = ?
E = hv = hc/λ = 6.62×10-34 3× 108 / 0.1 × 10-9
E = 1.98 × 10-17 J = 124.25 eV
Momentum of the photon is
p = h/λ = 6.62 × 10-34 / 0.1 × 10-9
p = 6.62 × 10-24 kgms-1
QUE 10>Differentiate between Conductors, semiconductors and Insulators.
ANS>
QUE 11>Discuss the properties of photon.
ANS>Properties of Photon:
1. The existence of photon and electron are same in nature
2. The energy of one photon is E = h ν
3. The rest mass of the photon is zero and they travel with the speed of light
4. The relation between energy and momentum of a photon
E = cp
hν /c =p
5. Photons are not affected by either an electric field or magnetic field (i.e. they are electrically neutral)
QUE 12>Obtain an expression for fringe width in case of Interference phenomena of light. Prove that in this case of interference dark and bright bands are of equal width.
ANS> Let S be a narrow slit illuminated by monochromatic light and S, and S, be two parallel slits very close together and equidistant from S. The light waves from S, an S, produce an interference pattern on a screen XY placed parallel to S, and S, as shown in.
(S2P)2=(S2M2)2+(PM2)2=D2+(x+d)2=D2[1+(x+d)2D2]
S2P=D[1+(x+d)2D2]1/2
Since D>> (x+d), the binomial expansion up to two terms will give
S2P=D[1+(x+d)2D2]1/2
=D[1+12(x+d)2D2]
=D+(x+d)22D
S1P=D+(x–d)22D
S2P–S1P=2xdD
Now for maxima or bright fringes, the path difference in given by (S2 P – S1 P ) = nλ where n = 0, 1, 2
2xdD=nλ
x=nDλ2d
and For dark fringes, i.e, for minima the path difference in given by
S2P–S1P=(2n+1)λ2,wheren=0,1,2
2xdD=(2n+1)λ2
x=D2d(2n+1)λ2
Now let xn and xn+1 denote the distances of nth and (n + 1)th bright fringes, then
xn=nDλ2d
xn+1=(n+1)Dλ2d
Spacing between nth and (n + 1)th bright fringe or successive bright fringes is
xn+1–xn=(n+1)Dλ2d–nDλ2d
It is independent of n. Hence, spacing between any two consecutive bright fringes is same. Similarly, it can be shown that spacing between two consecutive dark fringes will also be Dλ/2d.
The spacing between any two consecutive bright and dark fringes is called the fringe width (β)
β=Dλ2d
QUE 13>What is Bright and Dark fringes? Two coherent sources are placed 1mm apart and generate interference fringes on a screen 0.9 m away.The second dark fringe is formed at a distance of 0.9mm from the central-fringe. Determine the wavelength of the monochromatic light used.
ANS>
QUE 14>Enumerate the various application of LASER in the field of science and engineering.
ANS>(1) It is used in fiber optic communication.
(2) Communication between planets is possible with laser.
(3) It is used in holography.
(4) It is used in underwater communication between submarines, as they are not easily absorbed by water.
(5) It is used to accelerate some chemical reactions.
(6) It is used to create new chemical compounds by destroying atomic bonds between molecules.
(7) It is used to drill minute holes in cell walls without damaging the cell itself.