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.

Q1) Why is the transmission of signals using sky waves, restricted to frequencies greater than 30 MHz.  (Marks 1)

Q8) How does magnetic induction of a paramagnetic substance vary with temperature.  (Marks 1)

Q9) Draw a labelled ray diagram to show the image formation in an astronomical telescope for a distant object.  (Marks 2)

Q11) The half-life of a radioactive sample in 30 seconds calculate (i) the decay constant & (ii) time taken for the sample to become 1/4th of its initial value  (Marks 2)

Q12) Describe the method of determining the surface temperature of a star.  (Marks 2)

Q19) Find the position of the object, which when placed in front of a convex mirror of focal length produces a virtual image which is half size of the object.  (Marks 3)

Q20) Explain with the help of a circuit diagram, how a potentiometer can be used to compare emf's of two primary cells. Write the formula used. 
(Marks 3)

Q24) State Seebeck effect. Mention two factors on which (i) neutral temperature (ii) temperature of inversion of a thermocouple depends. 
(Marks 3)