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Category: Architectural Acoustics

A  S  A = aS  a = AS

Description: The sound absorption coefficient a describes the property of a material to convert incident sound into other forms of energy - e.g. Thermal or Kinetic Energy; and thus to absorb it. Where, A = total equivalent sound absorbing area & S = total sound energy incident on it.

Category: Architectural Acoustics

CO = Depth of Sea = vt2

Description: Related to SONAR

Category: Architectural Acoustics

d = λu2, λu=Wavelength of ultrasonic wave

Description: The distance between adjacent nodal planes

Category: Architectural Acoustics

IL = KlogII0

Description: If K=1, then Intensity Level is expressed in a unit called "bel".

Category: Architectural Acoustics

I = QAt = 2π2f2a2ρv

Description: Amount of Sound Energy(Q) flowing per unit area. Where, t=time, a=amplitude, f=frequency, v=velocity, ρ=density of medium.

Category: Architectural Acoustics

L = K log10I

Description: Where, K = Constant. Note that Loudness is a physiological quantity. Equation is known as Weber-Fechner law.

Category: Architectural Acoustics

T = 0.167 VaS

Description: where, V = Volume of hall, a = absorption coefficient, S = Surface area.

Category: Architectural Acoustics

E = Em106 at t = T

Description: Sabine defined the reverberation time as the time taken by the sound intensity to fall to one millionth of its original intensity after the source stopped emitting sound.

Category: Architectural Acoustics

dLdI = KI

Description: Decreases with increase in intensity.

Category: Architectural Acoustics

v = fλu

Description: where, f = frequency of ultrasonic wave

Category: Architectural Acoustics

λu = 2nλsinθ

Description: where, θ is the angle of diffraction for the nth -order principle maxima

Category: Dielectrics

μ = q × x

Description: A pair of equal and opposite charges separated by a small distance(x) constitutes an electric dipole.

Category: Dielectrics

D = E + P

Description: Relation between Flux Density & Polarization.

Category: Dielectrics

E = Fq = kqr2

Description: Force that acts on a unit positive charge at a point.

Category: Dielectrics

E = Fq

Description: Force per charge. Where, F = force & q = charge. Units are Newton/Coulomb or N/C.

Category: Dielectrics

ϕ = EAcosθ

Description: Total number of electric field lines passing a given area in a unit time. Flux is Scalar. Where, E = Electric field & A = Area.

Category: Dielectrics

D = ΦA 

Description: Flux per unit area.

Category: Dielectrics

αe = 0r - 1N = 4π0R3

Description: Due to the presence of Electron. Obtained in Solids. Independent of Temperature. Where, N is Number of atoms per unit Volume.

Category: Dielectrics

χe = r - 1

Description: Ratio of Polarization to net electric field as modified by the induced charges on the surface of the dielectric. It' s Unit-less.

Category: Dielectrics

V = kqr, k(constant) = 1/4π0

Description: Determines the direction of charge flow between two conducting bodies when brought in contact. Where, Potential Energy can considered as U = qV.

Category: Dielectrics

P = Nμ

Description: Where, N = no. of electrons & µ = dipole moment

Category: Dielectrics

F = kq1q2r2

Description: where, r = distance between the center of two charges.

Category: Dielectrics

kE·ds = q

Description: For parallel plate capacitors.

Category: Dielectrics

q1q24π = μIdl*r4πr2   μ  1

Description: Ratio Between Electrical Induction & Dielectric Displacement Vector.

Category: Dielectrics

αi = e2ω21m + 1M

Description: Due to pressure of ions. Independent of Temperature. Where, ω = Natural Angular Frequency, m = Mass of anion, M = Mass of Cation.

Category: Dielectrics

P = Pe + Pi + Po + 0(Polrizability for Air) P = NαEint 

Description: Relation between all type of Polarizations.

Category: Dielectrics

λ = ql

Description: Charge per unit Length.

Category: Dielectrics

R = R1 + αt  -t

Description: Materials in which the Dielectric Polarization is linearly related to the electric field & the dielectric constant is not dependent on electric field. Where, α is Temperature Constant.

Category: Dielectrics

Ei = E + p30

Description: Total internal field for Dielectric.

Category: Dielectrics

(Number of atoms per unit cell * Number of electrons per atom) / volume of unit cell

Description: Unit : electrons/m^3

Category: Dielectrics

αo = μ2p3kBT

Description: Due to Orientation in a particular direction. Dependent on Temperature. Where, kB is Boltzman Constant.

Category: Dielectrics

μ  E  μ = αE  α(Polarizability) = μE

Description: Polarizability Constant known itself as Polarizability.

Category: Dielectrics

Pr = Pnv, Pn=Dipole Moment, v=volume

Description: An average dipole moment, per unit volume, called the Polarization Vector P (r ).

Category: Dielectrics

r = K = 

Description: Ratio : Permittivity of the medium / Permittivity of free space. Must be >>1.

Category: Dielectrics

σ = qA

Description: Charge per unit Area.

Category: Dielectrics

δ = qV

Description: Charge per unit Volume.

Category: Dielectrics

W = 12Vr - 1E2

Description: Energy stored in Dielectric field.

Category: Fiber Optics

α = sin-1n2core - n2cladding

Description: Maximum angle of the ray(against the fiber axis), hitting the fiber core which allows the incident light to be guided by the core.

Category: Fiber Optics

Θcritical = sin-1nrni, nr=Refractive medium, ni=Incident medium

Description: Angle is defined as the angle of incidence that provides an angle of refraction of 90-degrees

Category: Fiber Optics

NA =n2core - n2cladding

Description: It's the sign value of the Acceptance angle. It's the light gathering ability of the fiber.

Category: Laser

E = hf = hcλ

Description: where, h = plank constant(6.63*10^-34JS), c = Speed of light, λ = wavelength, f = frequency

Category: Laser

N2N1 = e-EKBT

Description: where, Kb = Boltzman Constant

Category: Laser

R12 B12N1ρ

Description: Where, ρ=density of incident radiation, B12 = probability of absorption of radiation per unit time, N1 = population of the lower energy level.

Category: Laser

Rsp =A21N2

Description: where, A21 = probability of spontaneous emission per unit time, N2 = population at higher energy level E2

Category: Laser

R21st = B21N2ρ

Description: where, B21 = probability of stimulated emission per unit time, ρ = density of incident radiation, N2 = population of higher energy level E2

Category: Magnetic Materials

μ = μ0μr

Description: µ of a medium is defined as the ability of the medium to allow the Magnetic Flux to penetrate through itself. Unit : H/m

Category: Magnetic Materials

μB = eh2me ,(h=1.055*10-34, me=Mass of electron, e=charge of electron)

Description: Value = 9.2771*10^-24. Smallest Unit of Magnetic Dipole Moment.

Category: Magnetic Materials

H = Fm

Description: It's a measure of the force experienced by an unit north pole when placed at a point in magnetic field. where, F = force, m = strength of one pole.

Category: Magnetic Materials

ϕ = BA

Description: It's the total number of lines of force emanating from the north pole of Magnet. where, B = Magnetic Induction, A = Area.

Category: Magnetic Materials

B = θA

Description: Magnetic flux passing through an unit area of cross section at that point. Unit : Tesla(T)

Category: Magnetic Materials

μm = m × l

Description: It's the measure of strength of the Magnet. where, m = strength of one of the pole, l = magnetic length in meter

Category: Magnetic Materials

χm = MH

Description: Shows how easily a substance can be magnetized. Unit-less. When (-ve) , solid is diamagnetic, high range - ferromagnetic, low range - paramagnetic

Category: Magnetic Materials

M = Magnetic MomentVolume

Description: Pole strength acquired per unit area of cross section of the specimen.

Category: Magnetic Materials

μ0 = μ = BH

Description: Ratio of Magnetic Induction B to the applied field H.

Category: Magnetic Materials

B = μ0H + M or μ = μ01 + χ or μr = 1 + χ

Description: Common relation among B, H, M, µ and χ

Category: Magnetic Materials

μr = μμ0   B = μ0μrH

Description: Permeability of any given medium is accessed relative to permeability of vacuum.

Category: Nanophysics

Circumference of tube = 3d·a2 +ab+b2

Description: where, d = distance between two nearest carbon atoms, a & b are the chiral lengths.

Category: Nanophysics

D = Circumference of the tube π

Description: Used for Carbon Nanotube

Category: Nanophysics

SA:V = 4πr243πr3 = 3r

Description: where, r = radious

Category: Superconductivity

Ic = 2πrHc

Description: Maximum current amount that destroys the superconducting property. It depends on the size of superconductor.

Category: Superconductivity

Jc = Ic/A

Description: Current Density corresponding to Critical Magnetic Field.

Category: Superconductivity

Hc = H01 - TTc2

Description: The minimum magnetic field required to destroy the superconducting state.

Category: Superconductivity

ν(Nu) = 2eVh

Description: where, V = Potential Difference, h = Planck's Constant

Category: Superconductivity

Tc  1/M

Description: "The transition temperature is inversely proportional to the square root of isotopic mass of single superconductor"

Category: Ultrasonics

f = 12πLC = 12lEρ

Description: LC represents Resonant Circuit. where, l = length of rod, E = elastic constant of rod, ρ = density

Category: Ultrasonics

f = p2lEρ

Description: Same as the frequency of vibration of rod but here, p = Young's Modulus


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