Time allowed : 3 hours 
Maximum Marks : 70

General Instructions :

(i) All questions are compulsory.
(ii) Marks for each question are indicated against it.
(iii) Question number 1 to 8 are very short-answer questions each of 1 mark. Answer them in about one sentence each.
(iv) Question number 9 to 18 are short-answer questions of 2 marks. Answer them in not more than 30 words each.
(v) Question number 19 to 27 are short-answer questions of 3 marks. Answer them in not more than 50 words each.
(vi) Question number 28 to 30 are long-answer questions of 5 marks each. Answer to these questions should be around 150 words each.
(vii) Use Log Tables, if necessary.
(viii) Please write down the serial number of the question before attempting it.

Q1) Give a reason to show that microwaves are better carriers of signals for long range transmission than radio waves.  (Marks 1)

Q2) How does the energy gap in an intrinsic semiconductor vary, when doped with a pentavalent impurity ?  (Marks 1)

Q3) State the condition in which terminal voltage across a secondary cell is equal to its e.m.f  (Marks 1)

Q4) Draw an equipotential surface in a uniform electric field.  (Marks 1)

Q5) If the number of turns of a solenoid is doubled, keeping the other factors constant, how does the self-inductance of the solenoid change ?  (Marks 1)

Q6) What is the ration of solar constants on the surfaces of two planets, whose surface temperatures are in the ratio 1 :2 ?  (Marks 1)

Q7) The wavelength of light coming from a distant galaxy is red-shifted. Is the galaxy receding or approaching the earth ?  (Marks 1)

Q8) What is the angle of dip at a place where the horizontal and vertical components of earth's magnetic field are equal ?  (Marks 1)

Q9) Briefly explain how the distance of an inferior planet from earth can be determined ?  (Marks 2)

Q10) Using Gauss' law, show that no electric field intensity exists inside a hollow charged conductor.  (Marks 2)

Q11) Four capacitors are connected as shown in the figure given below :

Calculate the equivalent capacitance between the points X and Y.  (Marks 2)

Q12) Draw the graph showing the variation of binding energy per nucleon with the mass number of different nuclei. State two inferences from this graph.  (Marks 2)

Q13) In a single slit diffraction experiment, if the width of the slit is doubled, how does the (I) intensity of light and (ii) width of the central maximum change. Give reason for your answer.  (Marks 2)

Q14) Draw the logic symbol of a 2-input NAND gate. Write down its truth table.  (Marks 2)

Q15) A ray of light passes through an equilateral glass prism, such that the angle of incidence is equal to the angle of emergence. If the angle of emergence is 3/4 times the angle of the prism, calculate the refractive index of the glass prism.  (Marks 2)

Q16) A concave mirror and a convex lens are held separately in water. What changes, if any, do you expect in the focal length of either ? (Marks 2)

Q17) A rectangular coil N turns and area of cross-section A, is held in a time-varying magnetic field given by B = B₀ sin t, with the plane of the coil normal to the magnetic field. Deduce an expression for the e.m.f. induced in the coil.  (Marks 2)

Q18) Draw the graph showing variation of thermo e.m.f. of a thermo-couple with the temperature difference of its junction. How does its neutral temperature vary with the temperature of the cold junction ?  (Marks 2)

Q19) Derive an expression for the electric potential at a point along the axial line of an electric dipole.  (Marks 3)

Q20) A copper voltameter is in series with a heater coil resistance 0.1 ohm. A steady current flows in the circuit for 20 minutes, and a mass of 0.99 gm of copper is deposited at the cathode. If the electro-chemical equivalent of copper is 0.00033 gm/coulomb, calculate the heat generated in the coil.  (Marks 3)

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