2012 - WAEC Physics Past Questions and Answers - page 3
21
A piece of copper of mass 20g at a temperature of 110oC was dropped into a mixture of ice and water at 0oC. If the final steady temperature of the mixture is 0oC . Calculate the amount of ice that melted [Specific heat capacity of copper = 0.4 Jg-1k-1, specific latent heat of fusion of ice = 330Jg]
A
0.37g
B
0.60g
C
2.40g
D
2.70g
correct option: d
Mice = (\frac{MC}{\theta})
= (\frac{20 \times 0.4 \times 110}{330} = 2.66)
22
Which of the following factors decreases the rate of evaporation of a liquid?
A
increase in pressure over the liquid
B
lowering the boiling point
C
decreasing in humidity
D
wind
correct option: a
Users' Answers & Comments23
When two waves are superimposed on each other, the following occurrences are possible, except
A
nodal lins
B
anti nodal lines
C
stationary waves
D
dispersion
correct option: d
Users' Answers & Comments24
Which of the following properties of waves is exclusive to transverse waves?
A
reflection
B
interference
C
diffraction
D
polarization
correct option: d
Users' Answers & Comments25
An object of height 2.5cm is places 20cm from a convex mirror of focal length 10cm. Calculate the height of its image
A
2.5 cm
B
3.0cm
C
5.0cm
D
25.0cm
correct option: a
(\frac{1}{v} = \frac{1}{f} - \frac{1}{u} = \frac{1}{10} - \frac{1}{2} = \frac{1}{20})
v = 20
but hi = (\frac{vxho}{u} = \frac{20 \times 2.5 }{20} = 2.5)
26
A to eater to glass to air to water to glass to air. Given that the refractive index for light passing from air to water is \(\frac{4}{3}\) and air to glass is \(\frac{3}{2}\), calculate the refractive index of glass relative to water
A
0.50
B
0.67
C
0.75
D
1.13
27
An object is placed at a point X between the focal point F and the optical centre C of a diverging lens. If F is the focal point on the other side of the lens, the image of the object is formed between
A
F and X
B
X and C
C
C and F
D
F and 2F
correct option: b
Users' Answers & Comments28
An object is placed 10cm from a converging lens of foal length 15cm. Calculate the magnification of the image formed
A
3.0
B
1.5
C
0.6
D
0.3
correct option: a
(\frac{1}{v} = \frac{1}{f} - \frac{1}{u})
(\frac{1}{15} - \frac{1}{10} = \frac{2 = 3}{30})
v = 30
but m = (\frac{v}{u} = \frac{30}{10} = 3)
29
A telescope is said to be in normal adjustment when the
A
focal length of he objective is greater than that of the eyepiece
B
focal length of the eyepiece is greater than that of the objective
C
focal length of the eyepiece is equal to that of the objective
D
objective focal point coincides wih that of the eyepiece
correct option: d
Users' Answers & Comments30
The sound heard by a person after the reflection of the sound generated by him is called
A
reverberation
B
resonance
C
echo
D
audibility
correct option: c
Users' Answers & Comments