OBAFEMI AWOLOWO UNIVERSITY
2006 POST UME TEST
INSTRUCTION: ANSWER ALL QUESTIONS
11. A convex lens of focal length of 10.0cm is used to form a real image whichis half the size of the object. How far is the object from the image?
12. A diverging lens of focal length 20cm forms an image half the size of the object. What is the object distance?
13. An object of height 3.00cm is placed 10cm in front of a biconvex lens of focal length 15cm. The image of the object is
(a) Real and 3.00cm tall
(b) Virtual and 3.00cm tall
(c) Virtual and 9.00cm tall
(d) Real and 9.00cm tall
14. The most suitable type of mirror used for the construction of a search light is the :
(a) Concave mirror
(b) Convex mirror
(c) Spherical mirror
(d) Parabolic mirror
15. Light waves and ripples of water are similar because both
(a) Are longitudinal waves
(b) Have the same velocity
(c) Can be diffracted and refracted
(d) Have the same frequency
16. Three 4-? resistors were connected in series by tola while ade connected the same set of resistors in parallel. The ratio of the value obtained by ade to that obtained by tola is
18. A coil of copper wire of N turns is kept rotating between the poles of a permanent magnet such that the magnetic flux linking the coil changes continuously. Which of the following statement is true?
(a) An emf is induced in the coil such that when the change of flux is positive the emf is positive, and when the change of flux is negative, the emf is negative.
(b) An emf is induced in the coil whose magnitude is inversely proportional to both the number of turns in the coil and the rate of change of magnetic flux.
(c) An emf is set up in the permanent magnet which reduces the flux in the coilto zero.
(d) A current flows in the coil and emf is set up proportional to both the rate of change of the flux and the number of turns.
19. The principle of operation of an induction coil is based on
(a) ohm's law
(b) Ampere's law
(c) Faraday's law
(d) Coulomb's law
20. The equation
150 62 X ? 150 63 Y + k + energy, represents
(a) ?- decay
(d) Photon emission
21. Which of the following radiation is a magnetic field?
(a) ?- rays (ii) ?-rays (iii) y-rays (iv) X- rays
(b) (i) and (ii) only
(c) (iii) and (iv) only
(d) (i) and (iii) only
22. The half –life of a radioactive element is 9 days. What fraction of atoms has decayed in 36 days? (a) ?
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