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CIE iGCSE Co-Ordinated Science P5.2.5 Applications and safety precautions Exam Style Questions Paper 3

CIE iGCSE Co-Ordinated Science Paper 3 - All Chapters

Question

(a) A scientist is studying a polar bear.
(i) State the minimum frequency audible to humans.
(ii) The scientist hears a loud sound of frequency 25 Hz. The sound has a wavelength of 14 m. Calculate the speed of this sound in air.
(iii) The polar bear jumps into a pool of water and makes water waves. Fig. 10.1 shows a wave.
Choose words from the list to identify Y and Z by completing the two sentences.
amplitude     frequency     pitch     trough     wave speed     wavelength
Y shows the              of the wave.
Z shows the              of the wave.
(iv) The scientist uses thermal imaging cameras to detect polar bears travelling on the ice. State the region of the electromagnetic spectrum detected in thermal imaging cameras.
(v) The scientist sees the polar bear under the water.
On Fig. 10.2, draw a ray of light to show how the light travels from the polar bear’s head to the scientist’s eye.
(b) In the Arctic, harmful ionising radiation reaches the Earth’s surface.
(i) State one danger to humans of ionising radiation.
(ii) α-particles, β-particles and γ-radiation are all types of ionising radiation. Place α-particles, β-particles and γ-radiation in order of their ionising effect, from most ionising to least ionising.

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

(a) A student walks to school.
Fig. 9.1 shows a speed–time graph for part of the journey.
(i) Write the letter C on a part of the graph where the student is walking at constant speed.
(ii) State a time when the student accelerates.
(iii) State the maximum speed of the student.
(b) In the classroom, the student uses a laptop computer.
Fig. 9.2 shows the power cable from the mains supply to the laptop.
The power cable insulation is damaged.
State one danger of using this laptop with damaged insulation.
(c) Fig. 9.3 shows a ray of light reflecting off the laptop screen.
(i) On Fig. 9.3, label the angle of incidence with the letter \(i\) and the angle of reflection with the letter \(r\).
(ii) State the relationship between the angle of incidence and the angle of reflection.
(d) The student watches the teacher demonstrate an experiment using the isotope strontium-90. Strontium-90 is radioactive and emits \(\beta\)-particles.
(i) State the charge on a \(\beta\)-particle.
(ii) State one method of storing safely a small quantity of strontium-90 in a school.
(e) Fig. 9.4 shows the student sitting on a chair.
Fig. 9.5 shows the student balancing on the chair which is tilted backwards.
Explain why the student and chair fall over when the chair is tilted further backwards. Use ideas about centre of gravity and moments in your answer.

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

• Topic P1.2 — Motion (Part (a))
• Topic P4.4 — Electrical safety (Part (b))
• Topic P3.2.1 — Reflection of light (Part (c))
• Topic P5.2.2 — The three types of nuclear emission (Part (d)(i))
• Topic P5.2.5 — Applications and safety precautions (Part (d)(ii))
• Topic P1.5.2 & P1.5.3 — Turning effect of forces & Centre of gravity (Part (e))

▶️ Answer/Explanation

(a)(i) C anywhere between t = 0 and t = 400 or between t = 440 and t = 800

Constant speed is shown by a horizontal line on a speed-time graph. The graph has two horizontal sections: from 0 to 400 seconds and from 440 to 800 seconds.

(a)(ii) anywhere from t = 400 s to t = 440 s

Acceleration is shown by a line with a positive gradient (sloping upwards). The graph shows this between 400 and 440 seconds, where the speed increases from 0.2 m/s to 0.4 m/s.

(a)(iii) 0.4 m/s

The maximum speed is the highest point on the graph, which is 0.4 m/s.

(b) electrocution/electric shock

Damaged insulation exposes the live wire inside the cable. If a person touches the exposed wire, they could receive an electric shock or be electrocuted, which can be fatal.

(c)(i) i and r labelled correctly on the figure

The angle of incidence (\(i\)) is the angle between the incident ray and the normal (a line perpendicular to the surface at the point of reflection). The angle of reflection (\(r\)) is the angle between the reflected ray and the normal.

(c)(ii) angle of incidence = angle of reflection

This is the law of reflection: the angle of incidence is always equal to the angle of reflection.

(d)(i) negative/minus 1 / –

Beta particles (\(\beta^-\)) are high-speed electrons emitted from the nucleus. They have a relative charge of -1.

(d)(ii) in a lead container

Radioactive sources should be stored in lead containers. Lead is dense and absorbs the radiation, shielding people from exposure. The container should also be labelled with a radiation warning symbol.

(e) The centre of gravity is not over the base; a moment is produced by the weight.

For an object to be stable, its centre of gravity must be above the area of its base. When the chair is tilted backwards, the centre of gravity moves outside the base. The weight of the student and chair then acts at a distance from the pivot (the edge of the base), creating a turning effect (moment). This moment causes the student and chair to fall over.

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