WAEC Physics 1999 past questions
Ten questions from the 1999 WAEC Physics paper, with answers and explanations. We hold 46 questions from this paper, and the Skolra app has all of them.
WAEC Physics 1999 questions and answers
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1.Thunder is usually heard some seconds after lightning is observed because
- Asound travels faster than light in air
- Blight travels much faster than sound in airCorrect
- Cthunder has a lower frequency than lightning
- Dlightning generates less energy than thunder
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Answer: B
Light travels at approximately 3 × 108 ms−1 while sound travels at only about 340 ms−1 in air.
Both lightning (light) and thunder (sound) are produced simultaneously by the same discharge. Because light reaches the observer almost instantaneously while sound takes roughly 3 seconds per kilometre, thunder is heard several seconds after the lightning flash.
- A
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2.The force between molecules of the same substance is termed
- Aviscosity
- Badhesion
- CcohesionCorrect
- Dsurface tension
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Answer: C
Cohesion is the force of attraction between molecules of the same substance (e.g., water–water). Adhesion is the force of attraction between molecules of different substances (e.g., water–glass). Surface tension is a consequence of cohesive forces at the surface of a liquid.
- A
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3.The half-life of a radioactive substance is
- Athe time for half the atoms in a radioactive sample to disintegrateCorrect
- Bthe reciprocal of the decay constant of the substance
- Cthe time for the activity of a radioactive sample to fall to zero
- Dthe time for the sample to lose half its original mass by evaporation
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Answer: A
The half-life (t½) of a radioactive substance is defined as the time taken for half the atoms (nuclei) in a given sample to decay (disintegrate).
It is related to the decay constant by: t½ = ln 2 / λ = 0.693 / λ. Note that 1/λ is the mean lifetime, not the half-life, so option B is incorrect.
- A
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4.A 10-Ω coil takes 21 s to melt 10g of ice at 0°C. Determine the current in the coil. (Specific latent heat = 336 Jg⁻¹)
- A2 A
- B8 A
- C4 ACorrect
- D6 A
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Answer: C
The electrical energy supplied equals the heat energy needed to melt the ice:
Q = mL = 10 × 336 = 3360 J
Electrical energy: E = I²Rt
3360 = I² × 10 × 21 = 210 I²
I² = 3360 ÷ 210 = 16
I = 4 A
- A
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5.Which of the following is not a safety precaution in a nuclear station?
- Aworkers wearing radiation-proof protective clothing
- Bassembling fissile material above the critical mass inside the reactor hallCorrect
- Cregular monitoring of radiation levels in and around the station
- Duse of thick lead and concrete shielding around the reactor
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Answer: B
Assembling fissile material above the critical mass would trigger an uncontrolled chain reaction — this is precisely what nuclear safety measures are designed to prevent.
Genuine safety precautions include:
• Lead and concrete shielding to absorb radiation.
• Protective clothing and dosimeters for workers.
• Continuous radiation monitoring.
• Proper storage and disposal of radioactive waste. - A
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6.A resistance wire of length 2 m and of uniform cross-sectional area 5.0 x 10-7 m2 has a resistance of 2.2 Ω Calculate its resistivity
- A5.5 × 10−7 Ω mCorrect
- B2.2 × 10−7 Ω m
- C11.0 × 10−7 Ω m
- D1.1 × 10−7 Ω m
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Answer: A
Resistivity is given by:
ρ = RA / L
ρ = (2.2 × 5.0 × 10−7) / 2
ρ = 11.0 × 10−7 / 2
ρ = 5.5 × 10−7 Ω m
- A
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7.The air column in a resonance tube is set into resonance by a vibrating tuning fork. The resultant waves will be
- Alongitudinal progressive waves
- Btransverse stationary waves
- Clongitudinal stationary wavesCorrect
- Dtransverse progressive waves
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Answer: C
Sound waves are longitudinal (compressions and rarefactions along the direction of propagation). When the tuning fork drives the air column at its resonant frequency, the incident and reflected waves superimpose to form a stationary (standing) wave. Therefore the resultant waves in the resonance tube are longitudinal stationary waves.
- A
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8.Iron at 30oC feels colder to the hand than wood at 28oC because
- Airon conducts heat away from the hand more rapidly than woodCorrect
- Bwood has a higher specific heat capacity than iron
- Ciron has a lower density than wood
- Diron is at a higher temperature than the wood
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Answer: A
Iron is a much better thermal conductor than wood. When you touch iron, heat flows rapidly from your hand into the iron, making it feel cold. Wood is a poor conductor (thermal insulator), so heat leaves the hand very slowly when touching wood, making it feel warmer despite being at a slightly lower temperature.
The sensation of cold is determined by the rate of heat loss from the hand, not just the temperature of the object.
- A
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9.In a uniform electric field, the magnitude of the force on a charge of 0.2 C is 4N. Calculate the electric field intensity
- A0.80 NC−1
- B4.00 NC−1
- C80.00 NC−1
- D20.00 NC−1Correct
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Answer: D
Electric field intensity is defined as the force per unit positive charge:
E = F/q = 4 ÷ 0.2 = 20 NC−1
- A
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10.The amplitude of a wave is the
- Aspeed at which the wave travels through the medium
- Bdistance between two successive crests of the wave
- Cnumber of complete oscillations per second
- Dmaximum displacement of a particle from its rest positionCorrect
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Answer: D
The amplitude of a wave is the maximum displacement of a vibrating particle from its equilibrium (rest) position. It is a measure of the energy carried by the wave — a larger amplitude means more energy.
- A
The questions come from past JAMB, WAEC and NECO papers. We use software to help write the answer options and explanations, and every answer is checked twice before it goes on the site. How we check
Spotted a wrong answer? Tell us from the app or on the contact page and we check it.
Practise all 46 questions we hold from the 1999 paper, on a timed CBT screen
Every question has the answer and an explanation, in the Skolra app.