PHYSICS – 2003 ,PAPER I, SECTION A

                    Time Allowed: Three Hours    Maximum Marks: 200

Candidates should attempt Questions 1 and 5 which are compulsory, and any Three of the remaining questions selecting at least ONE question from each Section.

SECTION A

1.       Answer any four of the following:

       (a)    Distinguish between resolving power and dispersive power of a grating What should be the resolving power f a grating to resolve two closely spaced wavelengths 4500 A and 4510 A.

      (b)   What is holography and how it is different from ordinary photography?

      (c)    The focal length of achromatic doublet made up of crown and flint glasses is 15 cm. Calculate the focal length of converging and diverging lenses of doublet if dispersive power of crown and flint glasses are 0.01506 and 0.02427 respectively.

     (d)   Explain the term phase velocity and group velocity what are its significance?

    (e)   Deduce an expression for the moment of inertia of a diatomic molecule separated by a distance ‘ϒ’ about an axis passing through the centre of mass and perpendicular to the bond length and also along the bond length.

2.       (a) Discuss the motion of a particle under a central force field. Find the condition under which the orbit will be ellipse or parabola or hyperbola.

                  (b)  An artificial earth satellite is travelling at an altitude of 150 kms above the earth’s surface where g= 9.5 m/ sec². Calculate the speed of the satellite (radius of the earth – 6000 km).

3.       (a) (i) Derive the formula for variation of mass with velocity.

                        (ii) A rod f length 1 m in a spaceship is moving with a velocity of 0.3 C relative to the earth. Calculate its length as measured by an observe first on the spaceship and on the earth.

                 (b)  Deduce an expression for total energy of a simple harmonic oscillator. Show that total energy remains independent of time and displacement. Write a note on the effect of damping on the total energy of oscillator.

4.       (a) Discuss the principle off Frenels’ half period zones and explain how these are used in the construction of a zone plate. Show that zone plate has several foci.

                   (b)  (i) Discuss briefly some applications of Michelson enterferrometer.

                         (ii)  Lycopodium spores which have an average diameter of 30 µ m are dusted, on a glass plate. If parallel light of l = 589 nm is passed through the plate, what is the angular radius of first diffractions maximum?