1998 - WAEC Physics Past Questions and Answers - page 3

21
A waterfall is 1.260m high. Calculate the change in temperature of a quantity of water that falls from the top to the bottom of the waterfall. (Neglect heat losses to the surroundings, take g as 10m-2 and specific heat capacity of water as 4200Jkg-1K-1)
A
0.3oC
B
3.0oC
C
33.3oC
D
42.0oC
22
A piece of metal is heated until it becomes red-hot, it is then quickly transferred into a beaker containing boiling water. What effect will this have on the boiling water?
A
the boiling water rises slightly
B
the boiling point rises sharply
C
the rate of vaporisation of the boiling water increases
D
the boiling point first rises and then falls
23
A 90-W immersion heater is used to supply energy for five minutes. The energy supplied is used to completely melt 180g of a solid at is melting point. Neglecting energy losses to the surroundings, calculate the specific latent heat of fusion of the solid
A
0.5Jg-1
B
2.5Jg-1
C
15.0Jg-1
D
450.0Jg-1
24
If an ebonite rod is rubbed with fur
A
both the ebonite rod and the fur will be negatively charged
B
the ebonite rod will be positively charged while the fur will have no charge
C
there will be electron transfer only if the ebonite rod is earthed
D
the ebonite rod will be negatively charged while the fur will be positively charged
25
An eclipse of the sun by the moon occurs when the sun, the moon and the earth are in a straight line and the
A
earth casts a shadow on the moon
B
moon casts a shadow on the sun
C
moon is between the sun and the earth
D
earth is between the sun and the moon
26
The phenomenon which occurs when light changes direction as it passes from one medium to another is called
A
reflection
B
polarisation
C
interference
D
diffraction
27
What is the image distance of an object placed at a distance of 2f from a converging lens of focal length f?
A
f/4
B
f/2
C
f
D
2f
28
The images formed by diverging lenses are always
A
diminished, virtual and inverted
B
diminished, virtual and errect
C
diminished inverted and real
D
magnidied, virtual and errect
29
A converging lens of focal length 5cm is used as a magnifying glass by a man whose nearpoint is 35cm. Calculate the magnification given by the lens
A
8
B
7
C
6
D
5
30
An astronomical telescope having an objective of focal length 100cm and an eyepiece of focal length 10cm is used in normal adjustment, calculate the separation of the lenses
A
0.10m
B
0.90cm
C
1.10m
D
1.80m
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