Visvesvaraya Technological University (VTU) 2011-2nd Sem B.E This is a format which lecturer's can make use of and students too for their preparation.This can used by all the physics lecturers worki

I SEMESTER I INTERNAL exam (2011-2012)
ENGINEERING PHYSICS (10 PHY 12)
Max Time: one hour Max Marks: 25

Part A
1 (a) define Davisson-Germer experiment to prove the dual nature of matter waves. (5 Marks)
(b) describe group velocity. Derive relation ranging from group velocity and phase velocity.
(5 Marks)
Or
2 (a) define the ultraviolet catastrophe. (2 Marks)
(b) describe group velocity and find an expression for the identical. (3 Marks)
(c) A particle of mass 0.65 MeV/c2 has a kinetic energy 80 eV. obtain the de-Broglie wavelength, group velocity and phase velocity of the de-Broglie wave. (3 Marks)
(d) In a photocell illuminated by light of frequency five ×1014 Hz, a reverse potential of two Volts is needed to stop the photoelectron emission. obtain the work function of the material of the emitter. (2 Marks)


Part B

3 (a) define the construction and working of Semiconductor laser (5 Marks)
(b) find an expression for energy density of radiation under equilibrium condition in terms of Einstein co-efficient (5 Marks)

Or

4 (a) define briefly the application of lasers in welding. Mention its advantages over conventional welding (2 marks)
(b) Write a note on measurement of pollutants in atmosphere using laser. (3 Marks)
(c) Briefly discuss how, by changing the directions of view, various perspectives of the object are observed through a hologram (2 Marks)
(d) The transition to the ground state from the upper and lower energy states in a ruby laser outcomes in the emission of photons of wavelength 692.8nm and 694.3 nm respectively. Estimate the energy values of the 2 energy levels in eV (3 Marks)




Part C
ans all the ques.
5. In a blackbody radiation spectrum, the Wien's distribution legal regulations is applicable only for
A) Longer wavelength B) Shorter wavelength C) Entire wavelength
D) None of these

6. If the group velocity of de-Broglie wave is 4×108 m/sec, its phase velocity is
A) 12×108 m/sec B) 2.25×108 m/sec C) 5.33×108 m/sec D) 1.33×108 m/sec

7. The Compton wavelength is provided by
A) h/m0C2 B) h/m0C C) h2/m0C2 D) h2/2m0C

8. Electrons behaves as waves because they can be :
A) Deflected by an electric field B) Diffracted by a crystal
C) Deflected by magnetic field D) They ionize a gas

9. If the momentum of a particle is increased to 4 times, the de-Broglie wavelength is
A) become one-fourth B) become for times C) become twice D) become half

10. Which colour comes out from He-Ne laser
(A) Blue (B) Green (C)White (D) Red

11. The depopulation of 1s state in Ne atoms in a He-Ne laser is made efficient by
(A) Driving small discharge current (B) Increasing the portion of neon gas in the tube
(C) Increasing the length of the tube (D) Decreasing the diameter of the of the tube

12. Which 1 of the subsequent is false
(A) Very high pump power needed in 3 level laser system
(B) Semiconductor laser is not an example of 3 level laser system
(C) Population inversion can easily achieved with lower pumping requirements in 4 level laser systems
(D) Ruby laser is an example of 4 level laser system

13. The popular line of He-Ne laser is
(A) 623.8 nm (B) 694.3 nm (C) 3.39 ?m (D) 632.8 nm

14. In order to see the image of an object recorded by holography
(A)It is enough if we just have hologram
(B) We need the hologram, the reference beam and the object beam
(C) We need both the hologram and the reference beam
(D) We need the hologram, the reference beam, the object beam as well as the object
(10 × ½ = five marks)

Earning:   Approval pending.