1994 - JAMB Physics Past Questions and Answers - page 3
21
The sound from a source travelled to the bottom of the sea and the echo was heard 4s later. If the speed of sound in sea water is 1500ms-1 the depth of the sea is
A
6000m
B
3000m
C
1500m
D
375m
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22
The fundamental frequency of vibration of a sonometer wire may be halved by
A
doubling the length of the wire
B
doubling the mass of the wire
C
reducing the tension by half
D
reducing the absolute temperature by half
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23
A pipe of length 45cm is closed at the end. Calculate the fundamental frequency of the sound wave generated in the pipe if the velocity of sound in air is 360ms-1 [Neglect end correction]
A
5.5Hz
B
148.5Hz
C
200.0Hz
D
550.0Hz
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24
The note produced by a stretched string has a fundamental frequency of 400Hz. If the length of the string is doubled while the tension in the string is increased by a factor of 4, the frequency is
A
200Hz
B
400Hz
C
800Hz
D
1600Hz
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25
To produce a parallel beam of light from a concave mirror, the distance at a which the lamp should be placed from the mirror is equal to
A
the focal length
B
two times the focal length
C
the distance of the image
D
two times the radius of curvature
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26
Light of frequency 6.0 x 1014 Hz travelling in air is transmitted through glass or refractive index 1.5. Calculate the frequency of the light in the glass
A
4.0 x 1014Hz
B
6.0 x 1014Hz
C
7.5 x 1014Hz
D
9.0 x 1014Hz
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27
An object is placed in front of a converging lens of a focal length 20cm. The image is virtual and has a magnification of 2. What is the distance of the object from the lens?
A
5cm
B
10cm
C
30cm
D
40cm
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28
An object is placed directly below a glass block of thickness 3.0cm. Calculate the lateral displacement of the object if the refractive index of the glass is 1.5.
A
1.0cm
B
1.5cm
C
2.0cm
D
2.5cm
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29
In a projection lantern of focal length f, the object distance u, is such that
A
u > 2f > f
B
u < f < 2f
C
u = f < 2f
D
f < u < 2f
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30
If the Nigeria flag (green, white, green) is viewed in pure yellow light, which of the following set of colours would be observed on the flag?
A
Green, yellow, green
B
Red, yellow, red
C
black, yellow, black
D
Green, white, green
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