## Applied Physics 2 - Dec 2015

### 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 of the following

**1 (a)** Fringes of equal thickness are observed in a thin glass wedge of R.I-1.52. The fringe spacing is 1mm and wavelength of light used is 5893Å. Calculate the angle of the wedge.(3 marks)
**1 (b)** What is meant by diffraction? State its type and differentiate them.(3 marks)
**1 (c)** The core diameter of multimode step index fibre is 50 μm. The numerical aperture is 0.25. Calculate the no. of guided modes at an operating wavelength of 0.75μm.(3 marks)
**1 (d)** Differentiate spontaneous and simulated emission process related to laser operation.(3 marks)
**1 (e)** How is phase difference between two A.C. signals measured by CRO?(3 marks)
**1 (f)** What is De-Broglie wavelength of an electron which has been accelerated from rest through a potential difference of 100V?(3 marks)
**1 (g)** How can the 'Maglev' train have very high speed?(3 marks)
**2 (a)** Show that the diameter of Newton's n^{th} ring is directly proportional to square, root of ring number. In a Newton's ring pattern one of the dark ring due to light of wavelength 7000A°. Is found to coincide with the dark right of next order due to 5000A°. If the radius of curvature of the lens is 148.8cm. Find the diameter of the overlapping darking.(8 marks)
**2 (b)** Define :

i) Numerical aperture

ii) Total internal reflection

iii) Acceptance angle

Derive the expression for numerical aperture of step index fibre.(6 marks)
**3 (a)** What is Holography? Explain the construction and reconstruction of Hologram with neat diagrams.(8 marks)
**3 (b)** Why are the fringes in Wedge shaped film straight? Derive the conditions of maxima and minima for interference in wedge shaped film.(7 marks)
**4 (a)** A diffraction grating used at normal incidence gives a yellow line (λ=6000 A°) in a certain spectral order superimposed on a blue line (λ=4800 A°) of next higher order. If the angle of diffraction is sin^{-1} (3/4), Calculate th grating element.(5 marks)
**4 (b)** Derive Schrodinger's time-independent wave equation.(5 marks)
**4 (c)** Differentiate Type-I and Type-II super conductor.(5 marks)
**5 (a)** The visible spectrum ranges from 4000 A° to 7000 A°. Find the angular breadth of the first order visible spectrum produced by a plane grating having 6000 lines/cm when light is incident normally on the grating.(5 marks)
**5 (b)** Show that the energy of an electron in a box varies as the square of the natural number.(5 marks)
**5 (c)** What are carbon-nano tubes? Explain its properties?(5 marks)
**6 (a)** With single slit electron diffraction, prove Heisenberg's uncertainty principle.(5 marks)
**6 (b)** Explain the principle, construction and working of CRT with neat diagrams.(5 marks)
**6 (c)** Explain the top down approach and bottom up approach to prepare nanomaterials.(5 marks)