An atom radiates 1.5 x \(10^{-19}\)J of energy when an electron jumps from one energy level to another. What is the wavelength of the emitted radiation? (Planck’s constant =6.6 x \(10^{-34}\)Js. Speed of light in air=3 x \(10^{8}ms^{-1}\)
A1.32 x \(10^{-6}\)m
B2.98 x \(10^{-6}\)m
C3.32 x \(10^{-6}\)m
D6.82 x \(10^{-6}\)m
E8.01 x \(10^{-6}\)m
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Question 2
waec1997
In a nuclear reaction, the mass defect is 2 x \(10^{-6}\)g. Calculate the energy released given that the velocity of light is 3 x \(10^{8}ms^{-1}\)
A9 x \(10^{7}\)J
B1.8 x \(10^{8}\)J
C1.8 x \(10^{9}\)J
D9 x \(10^{-10}\)J
E3.6 x \(10^{11}\)J
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Question 3
waec1997
During the electrolysis of copper (II) tetraoxosulphate (VI) solution, an ammeter shows a steady reading of 1A for 30minutes while 6.6 x \(10^{-4}\)kg of copper is liberated. Calculate the error in the ammeter The electrochemical equivalent of copper is 3.30 x \(10^{-7}kgC{-1}\)
A0.001A
B0.011A
C0.111A
D1A
E1.1A
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Question 4
waec1997
A capacitor of capacitance 25µF is connected to an a.c power source of frequency 200/πHz. Calculate the reactance of the capacitor
A0.01Ω
B0.02Ω
C50Ω
D100Ω
E150Ω
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Question 5
waec1997
A charge of 1 x \(10^{-5}\)C experiences a force of 40N at a certain point in space. What is the magnitude of the electric field intensity at the point in Newton and couloumb
A8 x \(10^{6}\)
B4 x \(10^{6}\)
C3 x \(10^{-4}\)
D2 x \(10^{-4}\)
E5 x \(10^{-7}\)
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Question 6
waec1997
The current in a series R-L-C circuit attains its maximum value when the
AImpedance is greater than the capacitive reactance
BInductive reactance is equal to the capacitive reactance
CInductive reactance is greater than the capacitive reactance
Dcapacitive reactance is less than resistance
EInductive reactance is greater than the capacitive reactance
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Question 7
waec1997
A magnet is being inserted into a coil of wire. On which of the following factors does the induced e.m.f in the coil depend? I. Number of turns in the coil II. Strength of the coil III. Speed with which magnet is inserted into the coil.
AI only
BII only
CIII only
DI and II only
EI, II,III only
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Question 8
waec1997
The magnification produced with a converging lens is 5. If the object is a square wire gauze of side 2cm, calculate the area of the image
A100\(cm^2\)
B40\(cm^2\)
C20\(cm^2\)
D10\(cm^2\)
E4\(cm^3\)
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Question 9
waec1997
Which of the following is not true of the similarities between a camera and the human eye?
ABoth the camera and the human eye have light proof interiors
BBoth the camera and the human eye have light sensitive screens
CInverted images are formed on the screen in both
DThe distance between the lens and the screen is fixed in both
EThe amount of light entering both the eye and the camera can be adjusted
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Question 10
waec1997
The invisible part of the spectrum of a white light consists of the following colors
ARed, orange and yellow only
BInfra-red, ultraviolet and blue only
CIndigo and green only
DViolet and red only
EUltra violet and infra-red only
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Question 11
waec1997
An alternating current with a peak value of 5A passes through a resistor of resistance 10Ω. Calculate the rate at which energy is dissipated in the resistor
A250W
B125W
C50W
D35.4W
E12.5W
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Question 12
waec1997
A progressive wave has a wavelength of 50cm. calculate the phase difference between two points at a distance of 20cm apart.
A10/3π
B5/2 π
C4/5 π
D2/3 π
Eπ/3
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Question 13
waec1997
Which of the following statements is not correct?
AThe pitch of a note depends on the frequency of the vibrating source
BThe loudness of a note depends on its intensity
CThe velocity of sound in air does not depend on the intensity of the note producing it
DThe overtones present in a note determine its quality
EWind speed effects on the speed of sound in air
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Question 14
waec1997
A pipe open at both ends, produces a fundamental note. If the velocity of sound in air is V and L the length of the pipe, which of the following expresses the frequency of the note? Neglect end correction
A2V/L
BV/2L
CV/3L
DV/4L
EV/5L
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Question 15
waec1997
When a resistor of resistance R is connected across a cell, the terminal p.d of the cell is reduced to three quarters of its e.m.f. The internal resistance of the cell is expressed as
AR/4
BR/3
CR/2
D3R/4
E3R
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Question 16
waec1997
Two identical waves traveling in the same direction are superimposed. What should be the phase difference between the waves for maximum destructive interference to occur?
A20°
B45°
C180°
D225°
E270°
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Question 17
waec1997
In a photocell, light energy is converted to
AElectrical energy
BChemical energy
CHeat energy
DMechanical energy
EKinetic energy
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Question 18
waec1997
The current in the primary coil of a transformer is 2.5A. If the coil has 50 turns and the secondary250 turns, calculate the current in the secondary coil. Neglect energy losses in the transformer
A0.2A
B0.5A
C2.5A
D5A
E12.5A
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Question 19
waec1997
The relationship between the directions of magnetic field, the current-carrying wire in the field is easily remembered using
AOctet rule
BRight hand grip rule
CMaxwell’s screw rule
DAmpere’s swimming rule
EFleming’s left hand rule
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Question 20
waec1997
Lenz’s law of electromagnetic induction is essentially a statement of the
