Applied Physics 2 - May 2012

First Year Engineering (Semester 2)

TOTAL MARKS: 60
TOTAL TIME: 2 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Use suitable data wherever required.
(4) Figures to the right indicate full marks.

Attempt any five from the following:-

1 (a) Explain the effect on Newton's rings when oil (μ = 1.65) is introduced between the lens (μ = 1.5) and the glass plate (μ = 1.75).(3 marks) 1 (b) A grating has 620 rulings/mm and is 5.05mm wide. What is the smallest wavelength interval that can be resolved in the third order at λ = 481nm?(3 marks) 1 (c) Explain the terms: Stimulated emission and Population inversion.(3 marks) 1 (d) Calculate the De-Broglie wavelength of an electron whose kinetic energy is 120eV.
[m_e = 9.1x10^-31kg, h = 6.63x10^-34 J/sec].(3 marks) 1 (e) Distinguish between paramagnetic and ferromagnetic materials.(3 marks) 1 (f) Differentiate between step-index fibre and graded-index fibre.(3 marks) 1 (g) A magnetic material has magnetization of 2300 A/m and produces a flux density of 0.00314 Wb/m². Calculate the magnetizing force H and relative permeability of the material.(3 marks) 2 (a) Derive the conditions for a constant thickness film to appear bright and dark when being viewed in reflected light.(8 marks) 2 (b) Describe the construction and working of a He-Ne laser with schematic and energy level diagrams.(7 marks) 3 (a) What are anti-reflecting films? In costume jewelery, rhinestones (made of glass with μ = 1.5) are often coated with silicon monoxide (μ = 2.0) to make them more reflective. How thick should the coating be to achieve strong reflections for 560nm light, incident normally? (8 marks) 3 (b) What is holography? Explain construction and reconstruction of a hologram. (7 marks) 4 (a) Develop one dimensional time dependent Schrodinger equation for matter waves.(8 marks) 4 (b) Discuss Weiss's theory of ferromagnetism and derive Curie-Weiss's law.(7 marks) 5 (a) What is an optical resonator cavity? What role does it play in a laser beam? (5 marks) 5 (b) A mild steel ring having a cross-sectional area of 5cm² and mean diameter 20cm has a coil of 200 turns wound on it. Calculate the reluctance R and the current required to produce flux of 1mWb (μ_r = 380) neglecting air gap.(5 marks) 5 (c) An electron moves in the x-direction with a speed of 1.88x10⁶m/s. If this speed is measured to a precision of 1%, with what precision can you simultaneously measure its position? (5 marks) 6 (a) Explain the working principle of pirani gauge?(5 marks) 6 (b) Describe the working of scanning electron microscope (SEM) with diagram.(5 marks) 6 (c) What are hard and soft magnetic materials? Explain these materials using their characteristic properties and applications. (5 marks) 7 (a) What is meant by numerical aperture of an optical fibre? An optical fibre has a numerical aperture of 0.20. Determine the acceptance angle for the fibre in water (μ = 1.33).(5 marks) 7 (b) A monochromatic light from He-Ne laser λ = 6328Å is incident normally on a diffraction grating having 6000 lines/cm. Find angles at which first and second order maxima would be observed. (5 marks) 7 (c) Newton's rings are observed in reflected light of wavelength 5 x 10^-5 cm. The diameter of 10^th dark ring is 0.5cm. Calculate radius of curvature R and thickness of film t at the ring.(5 marks)