Physics-1999-Set-II

Q1) Why is the transmission of signals using sky waves, restricted to frequencies greater than 30 MHz. (Marks 1)
Ans1) The transmission of signals using sky waves is restricted to frequencies greater then 30 MHz since lower frequencies are highly damped by interaction with matter.

Q8) How does magnetic induction of a paramagnetic substance vary with temperature. (Marks 1)
Ans8) The magnetic induction of a paramagnetic substance decreases with the increase in temperature.

Q9) Draw a labelled ray diagram to show the image formation in an astronomical telescope for a distant object. (Marks 2)
Ans9) Ray diagram of image formation by Astronomical telescope.

A”B” : Final image
O : Objective
E : Eye piece
d : least distance of distinct image

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)
Ans11) (i) T1/2 = 30 s
= 0.693/T1/2 = 0.693/30 = 0.0231 s-1
(ii) In 30 s, substance is reduced to half & in next 30s, it will be reduced to 1/4th
Hence time taken for substance to reduce to 1/4th of its initial value = 60 s

  1. No comments yet.
  1. No trackbacks yet.