RTU Previous Question Papers BE 1st Semester Engineering Physics-1 July 2011

RTU Previous Question Papers BE 1st Semester

Engineering Physics-1 July 2011



1 (i) Explain the working of Michelson’s interferometer. How it is used to measure the difference in the wavelength between the D lines of sodium light?

(ii) Michelson interferometer experiment is performed with a source which have two wavelengths 4882 A and 4886 A. By what distance does the mirror have to be moved between positions of disappearance of fringes?

(i). Write short note on Interference filters.


1. (i) Explain the formation of Newton’s rings in reflected light. Why Newton’s rings are circular in shape, Explain.

(ii) Light containing two wavelengths Xl and X2 &Us normally on a piano convex lens of radius of curvature R resting on a glass plate. If the nth dark ring due to , coincides with the (n+l)th dark ring due to X2, prove that the radius of

(iii)Write short note on Anti-reflection coating.


2 .(i)  Show that plane polarised and circularly polarised light are the special cases of elliptically polarised light.

(ii) Intensity of light through a polariser and analyser is maximum when their principal planes are parallel. Through what angle the analyzer must be rotated so that the intensity gets reduced to 1/4 of the maximum value.

(ii) What is Malus Law?


(i)  Describe the construction and working of Laurent’s half shade polarimeter.

(ii) What are quarter wave and half wave plates? – Explain.

(iii) 80 gm of impure sugar when dissolved in a litre of water, gives an optical rotation of 9.9°, when placed in a tube of length 200 mm. If the specific rotation of sugar is 66 degree/dm / (gm/cc), find the percentage purity of sugar sample.


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

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

(iii) What is difference in Fresnel’s and Fraunhofer diffraction?


(i) Show that the intensity of light diffracted from a plane transmission grating is given by Where symbols have their usual meaning.

(ii) A diffraction grating just resolves lines 4547.27 A and 4547.98 A in third order. Will it resolve lines 6437.48 A and 6437.95 A in the first order?

(iii) Explain Rayleigh criterion of resolution.


4.  (i) Obtain an expression for shift in wavelength of the scattered photon by Compton scattering.

(ii) In compton experiment the wavelength of x-ray radiation scattered at an angle of 45° is 0.022 A. Calculate the wavelength of the incident x-rays.

(iii) Give physical interpretation of wave function.


4. (i) Write down Schrodinger’s equation for a particle confined in a one dimensional box. Obtain the wave function for a particle confined in this box.

(ii) A particle is moving in one-dimensional potential box of infinite height) of width 25 A. Calculate the probability of finding the particle within an interval of 5 A at the centres of the box when it is in its state ot least energy.

(iii) Explain normalized and orthogonal wave functions.


5. (i)  State the postulates of special theory of relativity and deduce from them the Lorentz Transformations.

(ii) Rocket A’ travels towards the right and rocket ‘B! travels to the left, with velocities 0.8 c and 0.6 c, respectively relative to the earth. What is the velocity of rocket A’ measured from rocket ‘B ?

(iii) Describe experiment verification of time dilation.


(i)  Derive Einstein’s mass energy relation and explain its importance.

(ii) Prove that particle having rest mass zero is always move with velocity of light.

(iii)If P and E represent the momentum and energy of a particle, then show that, under Lorentz Transformations, is an invariant.

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