# RTU Previous Year Question Papers BE First Year

# Physics-1 Feb 2010

Time : 3 Hours

Maximum Marks : 80

Min. Passing Marks : 24

Instructions to Candidates:

Attempt overall Five questions selecting one question from each unit. All questions carry equal marks.

**Unit -1**

1. a) Explain with the help of diagram and experiment arrangement to produce Newton’s rings.

b) What are the differences between fringes obtained in Newton’s ring experiment and those produced by a bi-prism.

c) In Newton’s ring experiment an air film is formed between two convex surfaces each of radius of curvature lm. Newton’s rings are generated by using a light of wavelength 5000 a . Find the distance between 16^{th} and 9^{th} dark rings.

**OR**

a) Explain the working of Michelson’s interferometer. How circular fringes be produced with it.

b) Show how Michelson’s interferometer is used to find the wavelength of light.

c) Write short note on

i) Antireflection coating and

ii) Interference filters.

**Unit-II**

2. a) What do you understand by the term ‘polarization of light’. Distinguish between polarized and unpolarized light in details.

b) What is meant by plane polarized, circularly polarized and elliptic ally polarized light. State Malus Law.

**OR**

a) Discuss double reflection in calcite crystal. How can a phase retardation plate be obtained from it.

b) Describe a polarimeter and explain how it is used to measure the strength of sugar solution.

**Unit-III**

3. a) Find out an expression for intensity at a point in a Fraunhufer diffraction due to single slit. Draw the intensity distribution curve,

b) The width of a slit is 0.012mm. Monochromatic light is incident on it. iThe angular position of first bright line is 5.2°. Calculate the wavelength of incident light.

**OR**

a) Deduce suitable formula to show the resolving power of a plane transmission grating depends on

i) Number of ruled lines and

ii) Width of ruled space

b) A sodium light consists of two lines of wavelength 5890 a and 5896 a Find the minimum number of lines that a grating must have in order to resolve their wavelength in first order..

**Unit-IV**

4 a) i)What is the difference between compton effect and photoelectric effect.

ii) Explain how compton scattering confirms the. quantum nature of radiation.

iii) Give reasons why the compton shift is detectable only in X-rays region and not in visible range of light.

b) Calculate the percentage of the maximum shift in the wavelength of incident

photons of wavelength 1a and 10 A due to compton scattering. What conclusion do you draw from this calculation.

**OR**

a) Derive Scrodinger’s time dependent wave equation. What is the physical significance of wave function used in this equation.

b) Determine the expectation value of position of a particle in one dimensional box.

**Unit – V**

5. a) State the postulates of special theory of relativity and deduce from them the Lorentz transformations.

b) Show that quantity (x^{2}+y^{2} + z^{2}-c^{2}t^{2}) is invarient under Lorentz transformation.

**OR**

a) Show that the relativistic kinetic energy is given by (m-m_{0})C^{2} and it

approaches to non-relativistic kinetic energy for v«c. (All symbols have their usual meanings).

b) Calculate the velocity of a particle at which its mass becomes twice of its rest mass.