CIE iGCSE Co-Ordinated Science P3.2.2 Refraction of light Exam Style Questions Paper 3
Question
Topic codes:
• Topic P3.4 — Sound (Part (a)(i) & (a)(ii))
• Topic P3.1 — General properties of waves (Part (a)(iii))
• Topic P3.3 — Electromagnetic spectrum (Part (a)(iv))
• Topic P3.2.2 — Refraction of light (Part (a)(v))
• Topic P5.2.2 — The three types of nuclear emission (Part (b)(ii))
• Topic P5.2.5 — Applications and safety precautions (Part (b)(i))
▶️ Answer/Explanation
(a)(i) 20 Hz
The range of frequencies audible to humans is approximately 20 Hz to 20,000 Hz (20 kHz). The minimum frequency audible is 20 Hz.
(a)(ii) 350 m/s
Wave speed is calculated using the equation: \(v = f \times \lambda\)
\(v = 25 \times 14 = 350\) m/s
(a)(iii) Y shows the wavelength; Z shows the amplitude
Wavelength (Y) is the distance between two consecutive crests or troughs. Amplitude (Z) is the maximum displacement of a point on the wave from its equilibrium position.
(a)(iv) Infrared
Thermal imaging cameras detect infrared radiation emitted by objects based on their temperature. Infrared is part of the electromagnetic spectrum with wavelengths longer than visible light but shorter than microwaves.
(a)(v) Ray of light travelling from the polar bear’s head to the surface; correctly refracted ray from the surface into the eye
When light travels from water to air, it bends away from the normal because it is travelling from a denser medium (water) to a less dense medium (air). The diagram should show:
- A straight ray from the polar bear’s head to the water surface
- The ray bending away from the normal at the water-air boundary
- The refracted ray continuing upwards to the scientist’s eye
(b)(i) Cell death / cancer / mutation
Ionising radiation has enough energy to remove electrons from atoms, damaging cells and DNA. This can lead to cell death, mutations, or the development of cancer. It can also cause radiation burns and damage to tissues.
(b)(ii) α → β → γ (most ionising to least ionising)
Alpha particles are the most ionising because they are large, heavy, and highly charged (+2). Beta particles are moderately ionising. Gamma radiation is the least ionising because it has no charge and is highly penetrating, passing through matter with less interaction.
Question
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P4.3.1 — Circuit diagrams and circuit components (Part (a)(i))
• Topic P4.2.4 — Resistance (Part (a)(ii))
• Topic P3.3 — Electromagnetic spectrum (Part (b))
• Topic P3.2.2 — Refraction of light (Part (c))
▶️ Answer/Explanation
(a)(i) Circuit diagram should show: 2 cells in series with a switch, lamp, and ammeter connected in series; voltmeter connected in parallel with the lamp.
The ammeter must be in series to measure the current through the lamp. The voltmeter must be in parallel with the lamp to measure the potential difference across it.
(a)(ii) Resistance = voltage ÷ current \(R = \frac{V}{I}\)
Ohm’s law states that resistance is the ratio of potential difference to current. The student calculates resistance by dividing the voltmeter reading by the ammeter reading.
(b)(i) X-rays → visible light → microwaves
The electromagnetic spectrum in order of decreasing frequency (or increasing wavelength) is: gamma, X-rays, ultraviolet, visible light, infrared, microwaves, radio waves. Visible light sits between ultraviolet and infrared. In the given boxes, between X-rays and microwaves, visible light is correctly placed.
(b)(ii) Gamma rays
Gamma rays have the highest frequency and shortest wavelength in the electromagnetic spectrum. They are produced by nuclear reactions and radioactive decay.
(c)(i) Normal
The normal is an imaginary line drawn perpendicular to the surface at the point where the incident ray strikes the boundary between two media.
(c)(ii) Refraction
Refraction is the change in direction of a light ray when it passes from one medium to another due to a change in its speed.
(c)(iii) The angle of incidence \(i\) should be labelled between the incident ray and the normal line XY.
The angle of incidence is measured between the incident ray and the normal, not between the ray and the surface.
(c)(iv) The emergent ray should be drawn parallel to the incident ray, leaving the glass block into the air.
When light passes through a parallel-sided glass block, the emergent ray is parallel to the incident ray but laterally displaced. The ray bends towards the normal when entering the glass (from air to glass) and bends away from the normal when leaving (from glass to air).