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Wednesday, 04 November 2026
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Physics Past Questions and Answers

Jamb 2009 Physics Questions

Question 31:
If the decay constant of a radioactive substance is 0.231s1, the half-life is?
  • A 3.00 s
  • B 0.12 s
  • C 0.33 s
  • D 1.50 s
View Answer & Explanation
Question 32:
A piece of radioactive material contains 1020 atoms.
If the half life of the material is 20 seconds, the number of disintegration in the first second is
  • A 3.47 x 10<sup style='font-size: smaller;'>18</sup>
  • B 6.93 x 10 <sup style='font-size: smaller;'>20</sup>
  • C 3.47 x 10<sup style='font-size: smaller;'>20</sup>
  • D 6.93 x 10<sup style='font-size: smaller;'>18</sup>
View Answer & Explanation
Question 33:
Thermionic emission is the process whereby
  • A β - rays are produced
  • B Holes are produced
  • C X - rays are produced
  • D Electrons leave a hot element
View Answer & Explanation
Question 34:
Which of the following can conduct electricity owing to the presence of free mobile electrons?
  • A Germanium
  • B Silicon
  • C Grapefruit
  • D Copper
View Answer & Explanation
Question 35:
When a pentavalent impurity is added to a pure semiconductor, it becomes
  • A A p-type semiconductor
  • B An n-type semiconductor
  • C An insulator
  • D An intrinsic semi-conductor
View Answer & Explanation