WAEC Physics 2007 past questions
Ten questions from the 2007 WAEC Physics paper, with answers and explanations. We hold 45 questions from this paper, and the Skolra app has all of them.
WAEC Physics 2007 questions and answers
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1.Which of the following wave is electromagnetic?
- ASound waves
- BRadio wavesCorrect
- CSeismic waves
- DWater waves
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Answer: B
Radio waves are part of the electromagnetic spectrum and do not require a medium for propagation. Sound waves, seismic waves, and water waves are mechanical waves that require a material medium to travel through.
- A
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2.A bulb marked 240V, 40W is used for 30 minutes. Calculate the heat generated
- A48 kJ
- B60 kJ
- C84 kJ
- D72 kJCorrect
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Answer: D
Heat generated equals the electrical energy converted: H = P × t
P = 40 W, t = 30 min = 30 × 60 = 1800 s
H = 40 × 1800 = 72 000 J = 72 kJ
Note: the voltage rating (240 V) is not needed here — power is already given.
- A
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3.In which of the following piece of apparatus is the radius of curvature equal to twice the focal length?
- AConcave lens
- BConcave mirrorCorrect
- CConvex lens
- DPlane mirror
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Answer: B
For a spherical mirror the focal length f = R/2, giving R = 2f. This direct relationship holds for a concave mirror (and convex mirror), making it the apparatus for which radius of curvature equals twice the focal length.
- A
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4.Which of the following statements is correct about resonance? Resonance occurs when a body
- Avibrates spontaneously without any external driving force
- Bis forced to vibrate at a frequency different from its natural frequency
- Cis forced to vibrate at the highest possible frequency
- Dis forced to vibrate at its natural frequencyCorrect
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Answer: D
Resonance occurs when the frequency of an applied driving force matches the natural frequency of the body. At resonance, energy transfer from the driver to the body is maximised and the amplitude of vibration increases greatly.
- A
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5.If a gas is excited by high voltage to produce a discharge and the light is examined in a spectrometer
- Aa dark-line absorption spectrum is observed
- Ba continuous spectrum of colours is produced
- Ca bright-line emission spectrum is observedCorrect
- Da broad band spectrum of colours is produced
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Answer: C
When a gas is excited by high voltage, its atoms absorb energy and electrons jump to higher energy levels. As electrons return to lower levels, they emit photons of specific frequencies.
In a spectrometer this produces a line emission (bright-line) spectrum — a series of bright coloured lines on a dark background, each line corresponding to a specific wavelength unique to that element.
A continuous spectrum comes from hot dense sources (e.g. incandescent solids); absorption spectra require a continuous source passing through cool gas.
- A
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6.A liquid of volume 2.00 m3 and density 1.00 x 103 is mixed with 3.00 m3 of another liquid of density 8.00 x 103kg m-3. Calculate the density of the mixture [Assuming there is no chemical reaction]
- A5.2 × 10³ kg m⁻³Correct
- B4.0 × 10³ kg m⁻³
- C2.0 × 10³ kg m⁻³
- D9.0 × 10³ kg m⁻³
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Answer: A
Mass of liquid 1: m₁ = 2.00 m³ × 1.00 × 10³ kg m⁻³ = 2 000 kg.
Mass of liquid 2: m₂ = 3.00 m³ × 8.00 × 10³ kg m⁻³ = 24 000 kg.
Total mass = 26 000 kg; total volume = 5.00 m³.
ρmix = 26 000 ÷ 5.00 = 5 200 kg m⁻³ = 5.2 × 10³ kg m⁻³. - A
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7.Which of the following surfaces will radiate heat energy best?
- Awhite shiny surface
- Bwhite dull surface
- Cblack dull surfaceCorrect
- Dblack shiny surface
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Answer: C
By Kirchhoff's law, good absorbers are also good emitters. A black, dull (matt) surface absorbs the most radiation and therefore also radiates heat energy most effectively. White or shiny surfaces reflect radiation and are poor emitters.
- A
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8.An object is placed 10cm in front of a plane mirror. If it is moved 8cm away father away from the mirror, determine the distance of the final image from the mirror
- A10 cm
- B18 cmCorrect
- C8 cm
- D26 cm
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Answer: B
Initial object distance = 10 cm. After moving 8 cm farther away, the new object distance = 10 + 8 = 18 cm. For a plane mirror the image distance always equals the object distance, so the final image is 18 cm from the mirror.
- A
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9.A car of mass 800kg moves from rest on a horizontal track and travels 60m in 20s with uniform acceleration. Assuming there were no frictional forces, calculate the accelerating force
- A240 NCorrect
- B480 N
- C80 N
- D120 N
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Answer: A
From rest, using s = ½at²: 60 = ½ × a × (20)² = 200a → a = 0.3 ms⁻².
Accelerating force: F = ma = 800 × 0.3 = 240 N. - A
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10.Which of the following phenomena is not a direct consequence of rectilinear propagation of light?
- ADispersion of white lightCorrect
- BWorking of a pinhole camera
- COccurrence of solar eclipse
- DFormation of shadows
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Answer: A
Shadows, eclipses, and the pinhole camera all occur because light travels in straight lines (rectilinear propagation). Dispersion of white light into its spectral colours is caused by refraction — different wavelengths bending by different amounts — and is not a consequence of rectilinear propagation.
- 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 45 questions we hold from the 2007 paper, on a timed CBT screen
Every question has the answer and an explanation, in the Skolra app.