# Mumbai University Previous year question papers

## Applied Physics-II

N.S. : (1) Question No.1 is compulsory.

(2) Solve any four questions from  a. Nos.2 to 7.

(3) Use suitable data wherever necessary.

1. \3olve ‘any five from the following :-

(a) What do you mean by thin film? Comment on the colours in thin film in sunlight.

(b) Define diffr~ction of light. Why is it not evident in daily experience?

(c) On the basis of magnetic dipoles of atoms explain the terms-ferromagnetism, antiferromagnetism and ferrimagnetism.

(d) Discuss the conditions required for a thin film to act as antireflection coating.

(e) Establish Bohr’s condition of quantization on the basis of de Broglie conception of matter waves.

(f) Calculate the de Broglie wavelength of a proton with a velocity equal to 20 th velocity of light. (mass of proton = 1.6 x 10-27 kg).

(g) What does LASER stand for? In what respects it differ from an ordinary source of light?

(h) Would you recommend optical fibres to be widely used in communication system? Why?

2. (a) How can Newton’s rings be obtained in the laboratory? Why do we get circular rings? Show that the radii of Newton’s nth dark rings is proportional to square root of Natural Number.

(b)’ White light is incident at an angle of 45° on a soap film 4 x10-5 cm’thick. Find the wavelength of light in the visible spectrum which will be absent in the reflected light (~ = 1.2).

3.

(a) Describe the construction of diffraction grating. What is grating element? How do you determine the wavelength of spectral line in the laboratory using plane transmission grating?

(b) A step index fibre has a core diameter of 29 x10-6 m. The refractive indices of core and cladding are 1.52 and 1.5189 respectively. If the light of wavelength 1.3 J..Lmis transmitted through the fibre, determine:

(i) normalised frequency of the fibre

(ii) the number of modes the fibre will support.

4.(a) What is de Broglie concept of matter maves? Derive one-dimensional time dependent Schrodinger equation for matter waves.

(b) In Fraunhofer diffraction due to a single slit of width 0.2 mm, a screen is placed 2 m away from the lens, to obtain the pattern. The first minima lie 5 mm on either side of the central maximum. Compute the wavelength of light.

5.

(a) With neat energy level diagram describe the construction and working of He-Ne Laser. What are its merits and demerits?

.(b) The magnetic susceptibility of silicon is –0.5 x 10-5. What is the intensity of magnetisation and magnetic flux density in a magnetic field of intensity 9.9 x 104 amp/m ?

6.

(a) Sketch the Hysteresis loop and explain the terms retentivity, coercivity, hysteresis and hysteresis loop. Give the characteristic properties and applications of Hard and Soft magnetic materials.

(b) An electron has a speed of 900 m/s with an accuracy of 0.001 %. Calculate the uncertainty with which the position of the electron can be located.

7.

(a) Explain what do you mean by biophysics? Discuss its importance. Mention the im?truments involved in this branch.

(b) Describe the role of vacuum in nanotechnology. List out the general applications of vacuum. .