2013 - WAEC Physics Past Questions and Answers - page 3
21
the equation of a certain progressive transverse wave is y = 2 sin 2 \(\pi ( \frac{1}{0.01} - \frac{x}{30})\), where x and y are in cm and t in seconds. Calculate the period of the wave
A
0.001s
B
0.010s
C
10.000s
D
100.000s
correct option: b
Compare: Y = 2 sin 2 \(\pi (\frac{1}{0.01} - \frac{x}{30})\)
y = 2 sin 2 \(\pi (\frac{1}{T} - \frac{x}{\pi}\))
\(\frac{t}{T} = \frac{t}{0.01}\)
T = 0.010s
Users' Answers & Commentsy = 2 sin 2 \(\pi (\frac{1}{T} - \frac{x}{\pi}\))
\(\frac{t}{T} = \frac{t}{0.01}\)
T = 0.010s
22
At which position should an object be placed in front of a concave mirror in order to obtain an image which is of the same size as the object?
A
at the centre of curvature
B
at the principal focus
C
between the pole and principal focus
D
between the centre of curvature and principal focus
correct option: a
Users' Answers & Comments23
Images formed by a convex mirror are always
A
magnified
B
behind the mirror
C
real
D
inverted
correct option: b
Users' Answers & Comments24
The refractive index of a material is 1.5. Calculate the critical angle at the glass-air interface
A
19o
B
21o
C
39o
D
42o
correct option: d
SinC = \(\frac{1}{n} = \frac{1}{1.5} = 0.6667\)
C = sin-10.6667
= 42o
Users' Answers & CommentsC = sin-10.6667
= 42o
25
A diverging lens of focal length 30cm produces an image 20cm from the lens. Determine the object distance
A
10cm
B
12cm
C
50cm
D
60cm
correct option: b
\(\frac{1}{v} + \frac{1}{v} = \frac{1}{f}\)
For a diverging lens, v is -ve, so we have
\(\frac{1}{u} - \frac{1}{v} = \frac{1}{f}\)
\(\frac{1}{u} = \frac{1}{f} + \frac{1}{v}\)
= \(\frac{1}{30} + \frac{1}{20} = \frac{2 + 3}{6}\)
u = \(\frac{60}{5} = 12cm\)
26
Which of the following statements about the Galilean telescope is not correct?
A
the final image is inverted
B
it is shorter than terrestial telescope
C
the final image is erect
D
it has a small field of view
correct option: a
Users' Answers & Comments27
Which of the following radiations has it's frequency lower than that of infrared radiation?
A
Utra-violet rays
B
gamma rays
C
x-rays
D
radio waves
correct option: d
Users' Answers & Comments28
a string under tension produces a note of frequency 14Hz. Determine the frequency when the tension is quadrupled
A
14Hz
B
18Hz
C
28Hz
D
56Hz
correct option: c
Users' Answers & Comments29
Which of the following statements about waves in pipes is correct?
A
for open pipes, there is only one end correction to be accounted for
B
for closed pipes, there are two end corrections to be accounted for
C
only odd harmonics are possible in closed pipes
D
all harmonics are possible in closed pipes
correct option: c
Users' Answers & Comments30
When a person holds a negatively charges metal rod and stands bare-footed on the ground, how will the charges leak?
A
negative charges flows to the ground through the person's body
B
positive charges flow from the ground through his body to neutralize the negative charges
C
positive charges in the air neutralizes the negative charges the person is holding
D
negative charges will leak through the air
correct option: a
Users' Answers & Comments