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Sant Gadge Baba Amravati University (SGBAU)
B.E. First Year Engineering (Applied Physics)
Engineering Physics - Winter 2024 Examination
Time: 3 Hours
Max Marks: 60
Roll No: _______________
there is no diagram in the actual question paper
SECTION - A
UNIT-1
Q.1 (a)
Prove that intrinsic semiconductor fermi level lies exactly at the middle of forbidden energy gap.
(5)
Q.1 (b)
Explain the working of P-N Junction in forward bias condition.
(3)
Q.1 (c)
State any four applications of light emitting diode.
(2)
OR
Q.2 (a)
What is Hall effect? Derive an expression for Hall Coefficient and mobility.
(4)
Q.2 (b)
Explain avalanche and Zener breakdown mechanism.
(3)
Q.2 (c)
Mobilities of holes and electrons in a sample of intrinsic semiconductor at room temperature are 1700 cm²/V-S and 3600 cm²/V-S. If electron and hole densities are each of equal to 2.5 × 10¹³ per cm³. Calculate conductivity.
(3)
UNIT-2
Q.3 (a)
What is Compton effect? Derive an expression for Compton shift.
(5)
Q.3 (b)
Give any four important properties of matter wave.
(2)
Q.3 (c)
Calculate the De-Broglie wavelength associated with a proton of mass 1.6 × 10⁻²⁷ kg moving with velocity equal to 1/20th of velocity of light.
(3)
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Q.4 (a)
State Heisenberg's uncertainty principle and show that electron does not exist inside the nucleus.
(4)
Q.4 (b)
Show that the De-Bronglie wavelength of Particle is λ = hc / √[k(k + 2m₀c²)].
(3)
Q.4 (c)
The wavelength of yellow light is 5890 Å. What is the energy of photon in the beam Express in electron volts?
(3)
UNIT-3
Q.5 (a)
Show that radius of semiconductor path of electron is directly proportional to momentum and inversely proportional to magnetic field.
(5)
Q.5 (b)
Draw a block diagram of cathode ray oscilloscope (CRO).
(3)
Q.5 (c)
An electron beam passes through a magnetic field of 2 × 10⁻³ Wb/m² and electric field of 3.4 × 10⁴ V/m both are acting simultaneously and path electron is undeviated. Calculate the speed of electron, if electric field is removed what will be the radius of electron path?
(3)
OR
Q.6 (a)
Describe the construction and working of Bainbridge mass spectrograph.
(4)
Q.6 (b)
Derive expression for vertical displacement of electron transverse electric field.
(4)
Q.6 (c)
An electron starts from rest and moves freely in an electric field of intensity 2400 V/m. Determine force on electron.
(2)
SECTION - B
UNIT-4
Q.7 (a)
Derive an expression for correct optical path difference in thin film due to reflected light. Also state the condition for constructive and destructive interference.
(5)
Q.7 (b)
How will you determine the Refractive index of liquid medium using newton's ring method.
(3)
Q.7 (c)
In newton's ring experiment the diameter of 20th dark ring changes from 1.5 cm to 1.39 cm, when liquid is introduced between lens and glass plate. Calculate refractive index of liquid.
(2)
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Q.8 (a)
Deduce an equation for radius of bright ring and show that it is directly proportional to square root odd natural numbers.
(4)
Q.8 (b)
What is plane diffraction grating? Give the theory of plane diffraction grating.
(3)
Q.8 (c)
Calculate the possible order of spectra with plane diffraction grating having 18000 lines per inch for λ = 4500 Å.
(3)
UNIT-5
Q.9 (a)
Derive an expression for acceptance angle and numerical aperture (NA).
(5)
Q.9 (b)
Write the application of optical fiber.
(3)
Q.9 (c)
An optical fiber has core material of refractive index of 1.55 and cladding of 1.50. Calculate the NA.
(2)
OR
Q.10 (a)
With neat labelled diagram explain the construction and working of Ruby Laser.
(4)
Q.10 (b)
Explain the absorption and bending loss in optical fiber.
(3)
Q.10 (c)
Find the loss specification of fibre length 500 m. If input is 8.6 μw and output power is 7.5 μw.
(3)
UNIT-6
Q.11 (a)
State and prove Bernoulli's theorem.
(5)
Q.11 (b)
What are ultrasonic? Write any four applications of ultrasonics.
(3)
Q.11 (c)
Write Sabine's formula for reverberation time and explain meaning of each term.
(2)
OR
Q.12 (a)
Define the following terms:
i) Reverberation.
ii) Reverberation time.
iii) Streamline flow.
iv) Stoke's law.
i) Reverberation.
ii) Reverberation time.
iii) Streamline flow.
iv) Stoke's law.
(4)
Q.12 (b)
What are the basic requirements of the acoustically good hall?
(3)
Q.12 (c)
A class room has dimension 20 × 15 × 5 m³. The reverberation time is 3.5 second. Calculate total absorption of its surface.
(3)
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IMPORTANT FORMULA SHEET
1. Mechanics & Dynamics
Moment = Force × Perpendicular Distance (M = F × d)
Varignon's Theorem: ΣM_o = M_R_o
Equilibrium: ΣFx = 0, ΣFy = 0, ΣM = 0
Lami's Theorem: P/sinα = Q/sinβ = R/sinγ
Varignon's Theorem: ΣM_o = M_R_o
Equilibrium: ΣFx = 0, ΣFy = 0, ΣM = 0
Lami's Theorem: P/sinα = Q/sinβ = R/sinγ
2. Modern Physics & Optics
Conductivity (σ) = n_i . e (μ_e + μ_h)
Compton Shift (Δλ) = (h/m₀c)(1 - cosθ)
De-Broglie λ = h/p = h/mv
Energy of Photon (E) = hν = hc/λ
Numerical Aperture (NA) = √(n₁² - n₂²) = n₁√2Δ
Compton Shift (Δλ) = (h/m₀c)(1 - cosθ)
De-Broglie λ = h/p = h/mv
Energy of Photon (E) = hν = hc/λ
Numerical Aperture (NA) = √(n₁² - n₂²) = n₁√2Δ
3. Acoustics & Fluid
Bernoulli's Eq: P + ½ρv² + ρgh = Constant
Sabine's Formula: T = 0.161 V / ΣaS
Stoke's Law: F = 6πηrv
Sabine's Formula: T = 0.161 V / ΣaS
Stoke's Law: F = 6πηrv
IMPORTANT DIAGRAMS (REFERENCE)
Simply Supported Beam
Lami's Theorem Force System
STUDENT NOTES
Use this space for rough work and calculations...
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