WAEC Physics 2018 past questions

Checked by the Skolra question team · Last updated 15 October 2026

Ten questions from the 2018 WAEC Physics paper, with answers and explanations. We hold 42 questions from this paper, and the Skolra app has all of them.

WAEC Physics 2018 questions and answers

1.
Rainbow formation is a natural phenomenon illustrating that white light
1. A
  is a mixture of colors
  Correct
2. B
  can be polarized
3. C
  can undergo total internal reflection
4. D
  travels in a straight line
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Answer: A
A rainbow forms when sunlight enters water droplets in the atmosphere and undergoes refraction and dispersion. The different wavelengths (colors) in white light refract by slightly different amounts, separating into a visible spectrum (ROYGBIV). This demonstrates that white light is a mixture of colors of different wavelengths.
2.State three materials used for making optical fibres.
1. A
  Copper, aluminium and silica
2. B
  Glass (silica), plastic (polymer) and fluoride glass
  Correct
3. C
  Quartz, copper and plastic
4. D
  Steel, rubber and glass
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Answer: B
Optical fibres are made from highly transparent materials that guide light by total internal reflection. The three main materials are:
- Silica glass (fused silica) — most common, low attenuation
- Plastic / polymer (e.g., PMMA — polymethyl methacrylate) — flexible, short-range use
- Fluoride glass — used for infrared transmission
3.
Which of the following statements about magnetic lines of force is not correct? They
1. A
  can intersect each other
  Correct
2. B
  form closed loops
3. C
  indicate the direction of the field
4. D
  emerge from the north pole
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Answer: A
Magnetic lines of force (field lines) never intersect each other. If they did, there would be two different field directions at a single point, which is physically impossible. All other statements are correct: they emerge from the N pole, enter the S pole, show the direction of the field, and form closed loops through the interior of the magnet.
4.
According to Newton's law of cooling, the heat energy lost per unit area of a body depends on the
I. Surface area
II. Nature of the surface
III. Temperature of the surface
IV. Excess temperature over the surroundings
1. A
  II and IV only
  Correct
2. B
  I and IV only
3. C
  III and IV only
4. D
  I and II only
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Answer: A
Newton's law of cooling states that the rate of heat loss per unit area is proportional to the excess temperature of the body above its surroundings (IV). The nature of the surface (II) (its emissivity/absorptivity) determines the constant of proportionality.
Surface area (I) is already divided out (heat loss per unit area), and temperature of the surface alone (III) is insufficient — it is the difference from the surroundings that drives cooling.
5.
Two plane mirrors are inclined to each other such that an object placed between them has 11 images. Determine the angle of inclination
1. A
  60°
2. B
  30°
  Correct
3. C
  45°
4. D
  36°
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Answer: B
Number of images formed by two inclined mirrors: n = (360°/θ) − 1
Given n = 11:
11 = (360°/θ) − 1
360°/θ = 12
θ = 360°/12 = 30°
6.
The primary of a transformer has 100 turns and its secondary has 200 turns. If the voltage at the primary is 100V, determine the voltage at the secondary.
1. A
  200 V
  Correct
2. B
  50 V
3. C
  100 V
4. D
  400 V
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Answer: A
For a transformer: V_s/V_p = N_s/N_p
V_s = V_p × (N_s/N_p) = 100 × (200/100) = 200 V
This is a step-up transformer since N_s > N_p.
7.
A wire of length 400cm is stretched between two fixed points. When plucked, its fundamental frequency is 150Hz. Calculate the speed of the wave produced.
1. A
  1500 m/s
2. B
  1200 m/s
  Correct
3. C
  600 m/s
4. D
  900 m/s
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Answer: B
For a wire of length L fixed at both ends, the fundamental frequency is:
f = v / (2L)
Rearranging: v = 2Lf
L = 400 cm = 4.0 m; f = 150 Hz
v = 2 × 4.0 × 150 = 1200 m/s
8.
A nuclide is represented by $_{32}^{70}B$ . Determine its neutron-proton ratio
1. A
  32/70
2. B
  19/16
  Correct
3. C
  16/19
4. D
  38/70
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Answer: B
For the nuclide ⁷⁰₃₂B: mass number A = 70, atomic number Z = 32 (protons).
Number of neutrons = A − Z = 70 − 32 = 38.
Neutron-proton ratio = 38/32 = 19/16.
9.
When the speed of a car is halved, its kinetic energy is
1. A
  quadrupled
2. B
  reduced to one half of its original value
3. C
  doubled
4. D
  reduced to one quarter of its original value
  Correct
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Answer: D
Kinetic energy KE = ½mv². If speed v is halved to v/2:
KE′ = ½m(v/2)² = ½m × v²/4 = KE/4
The kinetic energy is reduced to one quarter of its original value.
10.
Which of the following electromagnetic waves is most energetic?
1. A
  Gamma rays
  Correct
2. B
  Infrared radiation
3. C
  Radio waves
4. D
  Visible light
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Answer: A
The energy of an electromagnetic wave is given by E = hf, where h is Planck’s constant and f is frequency. Gamma rays have the highest frequency (and shortest wavelength) in the electromagnetic spectrum, and therefore each photon carries the most energy.

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

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WAEC Physics 2018 past questions

WAEC Physics 2018 questions and answers

Practise all 42 questions we hold from the 2018 paper, on a timed CBT screen

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