# Mumbai University Previous year question papers

## I Year Examination June 2009

## Applied Physics

N.B.1. Question No.1 is compulsory.

2. Attempt any four questionsfrom Q. Nos. 2 to 7. ..

3. Use suitable data whereverrequired.

4. Figures to the right indicate full marks.

5. Illustrateyour answerwith sketches wherevernecessary

1.(a) Draw the following for a Simple Cubic Structure :-

[212] [021] (00″2) ..

(b) Findthe shortestwavelenghtof X-rayproducedbyan X-raytube operatedat 16 kVof potential.

(c) Explain the term “Diamagnetism is the test for Super Conductivity”.

(d) Calculate the increase in the acoustic intensity level when the sound intensity is reduced to the half of original intensity.

(e) In phase measurement by Lissajous Pattern ellipse is obtained with major axis of 2 cm and minor axis of 0.8 cm estimate the phase angle.

2.(a) Determine the co-ordination number and packing density for a ‘Hexagonally Closed Packed’ structure. Show that a HCP structure demands an axial ratio of *‘J(8/3) *

(b) What is ‘Echo-Sounding’ ?

Velocity of Ultrasonics in mild-steel is 5.9 x 103m/s. The velocity of ultrasonic waves in brass measured by an ultrasonic gauge meter calibrated for miid steel is 4.3 x 103ml ‘sec. If thickness of a brass plate measured by the ultrasonic gauge meter is 15 cm what is real thickness?

3.(a) A sample of semiconductor is placed in uniform magnetic induction ‘B’ with sample current ‘i’ and thickness ‘t’ then obtain the expression for (a) Hall voltage (b) Hall coefficient and state. How to identify the type of semiconductor material.

(b) 10 KeV electrons are passed through a thin film of a metal for which atomic spacing is 5.5 x 10-11m. What is the angle of deviation of the first order diffraction minimum.

4.(a) Explain the concept of superconductivity. Explain following terms associated with superconductivity :-

(i) Critical Temperature

(ii) Critical Field

(iii) Type-I Super Conductor.

(b) What is Frankeldefect? How it is developed in a crystal? Estimate the ratio of Vacanctes at

(i) 119°C (ii) 80°C:.-Where average energy to create vacancy is 1.8 e.V.

5.(a)What is magnetostriction effect? Draw the diagram of magnetostriction oscillator arid explain its working as a ‘Ultrasound’ generator.

(b) Explain the concept of ‘holes’ as a majority ca(riers in P-type. Semiconductors. Explainconcept of mobility.”Calculate the mobility of electrons in Cu where resistivity of Cu .is 1.72x 10-8ohm-m and numberof electronsper unitvolume is 10.41x 10-28 per cubicmeter.

6.(a) How homogeneous beam of indentical charge particles can be prevented from divergence? Hence deduce the formula of Snell’s law for electron optics.

(b) class room has dimensions 20 x15 x 5 m3. Thereverbation tim~ i~ 3.5 secs. Calculate the total absorption of it’s surfaces and average absorption coefficient.

7. (a) .Explain following terms :-

(i) Phases of liquid crystal

(ii) Reverbation time

‘(iii) Characteristic X-ray spectrum.

(b) A CRT has anode voltage of 1.6 kV and parallel deflection plates are 1.8 cm long and 4.2 mm apart. The screen is at 2.8 cm from the centre of deflecting. plates. Find the input voltage required to deflect the beam by 1.5 em. The input voltage is applied to the deflection plates through the amplifiers having overall gain of 60.