2010 - WAEC Physics Past Questions and Answers - page 3
21
An electric drill rated 400W is used to drill a hole in copper of mass 400g in 20s. Calculate the rise in temperature if all the heat produced is absorbed by the copper. [specific heat capacity of copper = 400Jkg-1K-1]
A
100oC
B
75oC
C
50oC
D
45oC
correct option: c
\(\theta = \frac{Pt}{MC} = \frac{400 \times 20}{0.4 \times 400} = 50^o\)
Users' Answers & Comments22
A solid of mass 0.5kg initially at 50oC melts at 60oC. Calculate the quantity of heat required to melt it completely. [specific heat capacity of the solid =2.0KJ kg-1K-1][Specific latent heat of fusion of solid =1.0 KJ kg-1]
A
1500J
B
10000J
C
10500J
D
15000J
correct option: c
Q = ML + C\(\theta\)
= 0.5 x 1000 + 0.5 x 2000 x 10
= 10500
Users' Answers & Comments= 0.5 x 1000 + 0.5 x 2000 x 10
= 10500
23
Dew point is not affected by
A
temperature
B
wind
C
the amount of water vapour in the atmosphere
D
atmospheric pressure
correct option: d
Users' Answers & Comments24
A certain wave has a speed of 20ms-1. If the frequency of the wave is 0.25Hz, calculate the distance between successive crests of the wave
A
5.0m
B
40.0m
C
50.0m
D
80.0m
25
The ability of a wave to spread around corners is called
A
polarisation
B
dispersion
C
diffraction
D
reflection
correct option: c
Users' Answers & Comments26
The following devices use plane mirrors in their operations, except
A
periscope
B
sextant
C
kaleidoscope
D
binoculars
correct option: d
Users' Answers & Comments27
When an object is placed at the principal focus of a concave mirror, the location of the image formed is
A
between principal focus and pole
B
between principal focus and centre of curvature
C
at infinity
D
at centre of curvature
correct option: c
Users' Answers & Comments28
From the diagram, the correct equation for the refractive index n of the medium is
A
n = tan i
B
n = \(\frac{sin i}{sin 90^o}\)
C
n = \(\frac{sin i}{cos (90^o - i)}\)
D
n = sin 90oC
correct option: b
Users' Answers & Comments29
A ray of light travels from air to water. The refeactive index of water is given by the expression
A
\(\frac{\text{velocity in water}}{\text{velocity in air}}\)
B
\(\frac{\text{sine of angle of refraction}}{\text{sine of angle of incidence}}\)
C
\(\frac{\text{apparent depth}}{\text{real depth }}\)
D
\(\frac{\text{wavelength in air}}{\text{wavelength in water}}\)
correct option: d
Users' Answers & Comments30
A lens that is thinner at the middle and thicher at the edges is
A
diverging
B
converging
C
plano-convex
D
converging meniscus
correct option: a
Users' Answers & Comments