(i) Draw a ray diagram to show how the image of a distant object is formed by a refracting astronomical telescope when in normal use.
(ii) State one advantage of a reflecting astronomical telescope over a refracting astronomical telescope.
(i) What is meant by the term activity of a radioactive substance.
(ii) A radioactive sample has a half life of 1.4 x 1016 seconds and a mass number of 238. Calculate the number of disintegration/s of 1g of this sample.
Which of the radiations, α-rays, β-rays, or γ-rays are :
(i) easily absorbed by matter ?
(ii) similar to X-rays ?
The essential component of a reactor are as follows :
(i) Fuel: Uranium enriched with U235 or Pu239.
(ii) Moderator: The function of the moderator is to slow down the neutrons. Heavy water. Graphite or beryllium oxide is used as moderator.
(iii) Control rods : To control the chain reaction from becoming violent, rods of neutron absorbing materials like boron steel or cadmium can be inserted into the reactor core.
(iv) Coolant: The fusion product carry large kinetic energy with them. This is manifested as rise in temperature. Heat energy so produced is utilised in vapouring water or liquid sodium.
(v) Shielding: The entire reactor is provided with a thick concrete wall so that radiations emitted during the operation of a reactor may not be hazardous to a person in immediate vicinity.