41) A radioactive isotope decays at such a rate that after 96 mins only 1/8th of the original amount remains. The value of t _1/2 of this nuclide is:

a) 48 min
b) 25 min
c) 12 min
d) 32 min.

ANSWER : 32 min.

42) What is the half-life period of a radioactive substance if 87.5% of it disintegrates in 40 minutes?

a) 20 min
b) 13 min 20 sec
c) 160 min
d) 90 min 30 sec.

ANSWER : 13 min 20 sec

43) Which among the following is a positron?

a) ₊₁e⁰

b) ₁H¹

c) _-1e⁰

d) None of these.

ANSWER : ₊₁e⁰

44) Among the following, which Uranium is the most reactive?

a) ²⁴⁸U

b) ²²⁶U

c) ²³⁵U

d) ²³⁸U

ANSWER : ²³⁵U

45) Which of the following iodine is used in the treatment of thyroid disorders?

a) ¹³⁰I

b) ¹³¹I

c) ¹³²I

d) ¹²⁹I

ANSWER : ¹³¹I

46) …………..are the best bombarding particles.

a) Protons
b) Electrons
c) Positrons
d) Neutrons

ANSWER : Neutrons

47) A loss of ß-particle results in the production of:

a) Isotopes.
b) Isobars.
c) Isotones.
d) None of these.

ANSWER : Isobars.

48) The mass of an electron is:

a) 0.00055 a.m.u.
b) 1.0000 a.m.u.
c) 1.0078 a.m.u.
d) 1.0086 a.m.u.

ANSWER : 0.00055 a.m.u.

49) Relation between mass defect and binding energy is given by:

a) B.E. = Δm x 931 – M.
b) B.E. = Δm + 931.
c) B.E. = Δm x 931.
d) B.E. = [m + (A-Z) mn] – M

ANSWER : B.E. = Δm x 931.

50) Find the number of necleons present, if the binding energy of an element is 64 MeV. Given BE / Nucleon = 6.4.

a) 64
b) 10
c) 6
d) 16

ANSWER : 10  

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