# physics test

Jun 17th, 2015
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Q.1 1.02MeV positron collides with 1.02 MeV electron and they are annihilated giving rise to two y-photons, The total energy of y-photons is (A) 1.02 MeV (B) 2.04 MeV (C) 3,06 MeV (D) 4.08 MeV Q2 The activity of a radioactive substance at time t1 is A1 and at time t2 is A2, If the mean life of the substance is T m then the number of atoms

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PHYSICS MT-4Q.1 1.02MeV positron collides with 1.02 MeV electron and they are annihilated giving rise to two y-photons, The total energy of y-photons is(A) 1.02 MeV(B) 2.04 MeV (C) 3,06 MeV(D) 4.08 MeVQ2 The activity of a radioactive substance at time t1 is A1 and at time t2 is A2, If the mean life of the substance is T m then the number of atoms decayed during time interval (t2 - t 1 ) will be(A) A1t1 - A2 t2 (B) (A1 -A2)(C) (A1-A2)/ Tm(D) (A1-A2) Tm Q3. ?, ?, ? radiations come, but of a radioactive substance (A) When it is heated(B) When put in atomic reactor (C) Spontaneously(D) Under pressureQ.4 A radioactive element has undecayed (1/64) part in 15 hr. Its half kife in hrs will be(A) 2,5(B) 3,5(C) 7.5(D) 15Q.5. The fraction of a radioactive material which remains active after time t is 9/16, The fraction which remains active after time t/2 will be (A) 4/5(B) 7/8(C) 3/5(D) 3 / 4Q 6 .The half life of a radioactive material is 34.65 seconds. If at any time 1022 atoms are active, then the activity of that material is (A) 1 x 1020 disintegration/s (B) 2 x 1020 disintegration/s (C) 3 x 1020 disintegration/s (0) 4 x 1020 disintegration/sQ.7 Curie is a unit of (A) length(C) mass(B) its is not any unit (D) atomiC numberQ.9 The relation betvveen the mean life (?) and half life (T1/2) of a radioactive material is (A) ? = T1/2 / 0.693(B) ? = 0.693 / T1/2(C) ? = T1/2 x 0.693(D) none of theseQ10 Which of the following

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