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CIE iGCSE Co-Ordinated Science P3.2.1 Reflection of light Exam Style Questions Paper 3

CIE iGCSE Co-Ordinated Science Paper 3 - All Chapters

Question

(a) Fig. 12.1 shows four forces, A, B, C and D, acting on a car moving along a level road.
(i) State which force, A, B, C or D, is partly caused by air resistance.
(ii) One of the forces shown on Fig. 12.1 is the weight of the car.
Explain why the definition of weight below is incorrect.
“weight is a measure of the quantity of matter in an object”
(iii) The car is moving at constant speed. Force D is 2000 N.
State the value of force B. Explain your answer.
(b) As the car slows down the sound of the engine becomes quieter and the frequency of the sound waves decreases.
(i) State what happens to the amplitude of the sound waves.
(ii) State what happens to the pitch of the sound.
(c) The car has two identical headlamps P and Q, connected in a parallel circuit.
Fig. 12.2 shows the circuit diagram.
(i) State the name of the component in the circuit that causes a current to flow in the circuit.
(ii) The current in each lamp is 4 A. State the current at point X in the circuit. Choose from the values below.
0A      2A      4A      8A
Explain your answer.
(iii) State one reason why the headlamps in the car are connected in parallel rather than in series.
(d) The driver uses a plane mirror in the car to see an image of a bus behind the car.
Describe the characteristics of the image of the bus compared with the bus.

Most-appropriate topic codes (Cambridge IGCSE Coordinated Sciences 0654):

• Topic P1.5.1 — Effects of forces (Part (a)(i), (a)(ii), (a)(iii))
• Topic P3.4 — Sound (Part (b)(i), (b)(ii))
• Topic P4.3.2 — Series and parallel circuits (Part (c)(i), (c)(ii), (c)(iii))
• Topic P3.2.1 — Reflection of light (Part (d))

▶️ Answer/Explanation

(a)(i) D
Force D opposes the motion of the car and is partly caused by air resistance (drag), which increases with speed.

(a)(ii) weight is the gravitational force on an object that has mass / definition of mass (not weight)
The statement describes mass (the quantity of matter). Weight is the gravitational force acting on an object due to its mass in a gravitational field.

(a)(iii) 2000 (N) and (constant speed so) no resultant force
At constant speed, the driving force (B) equals the resisting force (D) because there is no resultant force and no acceleration. Therefore B = D = 2000 N.

(b)(i) decreases
The amplitude of a sound wave is related to loudness. A quieter sound has a smaller amplitude.

(b)(ii) decreases
Pitch is related to frequency. A lower frequency sound has a lower pitch. The engine note becomes lower in pitch.

(c)(i) battery
The battery provides the electromotive force (voltage) that causes current to flow through the circuit.

(c)(ii) 8 (A); current in main part of circuit is greater than current in either branch
In a parallel circuit, the total current from the source equals the sum of the currents in each branch. Current at X = 4 + 4 = 8 A.

(c)(iii) full voltage across both lamps OR if one lamp fails, the other will still work
Parallel connection ensures each lamp receives the full supply voltage and operates independently. If one fails, the other continues to work.

(d) any two from: same size; same distance from mirror; laterally inverted
A plane mirror produces an image that is: same size as the object, same distance behind the mirror as the object is in front, and laterally inverted (left-right reversed). The image is also virtual and upright.

Question

(a) Fig. 12.1 shows the circuit symbols for three electrical components, X, Y and Z, used in an electric torch (flashlight).
(i) Complete Fig. 12.1 to identify each component.
(ii) Using the symbols in Fig. 12.1, draw the circuit diagram for the torch.
(iii) The current in component Z is 0.50 A. The voltage supplied by component X is 1.5 V. Calculate the resistance of component Z.
(b) Fig. 12.2 shows a single ray of light from the torch reflected by a mirror.
(i) State the name of the dotted line AB.
(ii) On Fig. 12.2, label the angle of incidence with the letter \(i\).
(iii) The angle of incidence is 40°. State the angle of reflection.
(c) Fig. 12.3 shows a single ray of white light from the torch passing into a glass prism.
Complete Fig. 12.3 to show what happens to the light as it passes through and out of the prism.

Topic codes:

• Topic P4.3.1 — Circuit diagrams and circuit components (Part (a)(i) & (a)(ii))
• Topic P4.2.4 — Resistance (Part (a)(iii))
• Topic P3.2.1 — Reflection of light (Part (b)(i), (b)(ii) & (b)(iii))
• Topic P3.2.4 — Dispersion of light (Part (c))

▶️ Answer/Explanation

(a)(i) X is a cell; Y is a switch; Z is a lamp
The cell provides the electrical energy (voltage). The switch controls the flow of current by opening or closing the circuit. The lamp (bulb) converts electrical energy into light and heat energy.

(a)(ii) All 3 components connected in series
In a simple torch circuit, the cell, switch, and lamp are connected in series so that current flows through all components in a single loop. When the switch is closed, the circuit is complete and the lamp lights up.

(a)(iii) Resistance = 3.0 Ω
Using Ohm’s law: \(R = \frac{V}{I}\)
\(R = \frac{1.5}{0.50} = 3.0\) Ω

(b)(i) Normal
The normal is an imaginary line drawn perpendicular (at 90°) to the reflecting surface at the point where the incident ray strikes the mirror.

(b)(ii) Angle of incidence labelled correctly
The angle of incidence is the angle between the incident ray and the normal. It should be labelled with the letter \(i\) between the incoming ray and the normal line AB.

(b)(iii) Angle of reflection = 40°
According to the law of reflection, the angle of incidence equals the angle of reflection. Both angles are measured from the normal. Therefore, if the angle of incidence is 40°, the angle of reflection is also 40°.

(c) Correct refraction through and out of the prism; dispersion shown on entry to the prism
When white light enters a glass prism, it slows down and bends (refracts). Different colours of light have different wavelengths and are refracted by different amounts, causing the white light to split into its component colours (dispersion). The spectrum is produced in the order: red, orange, yellow, green, blue, indigo, violet. The ray diagram should show:

  • The ray bending towards the normal when entering the prism (from air to glass)
  • The ray spreading into a spectrum (dispersion) at the first surface
  • Each colour ray bending away from the normal when exiting the prism (from glass to air)
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