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CIE iGCSE Co-Ordinated Science P5.2.2 The three types of nuclear emission Exam Style Questions Paper 3

CIE iGCSE Co-Ordinated Science Paper 3 - All Chapters

Question

A house has an electric doorbell.
(a)(i) Draw a circuit diagram to show a doorbell connected in series with a switch and a battery.
Use the circuit symbol, , for the doorbell.
(ii) The battery has four 1.5 V cells in series. When the bell rings the current in the bell is 3.0 A.
Calculate the resistance of the bell.
(b) The house is fitted with a household fire (smoke) alarm.
The smoke detector in the alarm contains a radioactive isotope of americium-241 which emits α-particles.
(i) State the composition of an α-particle.
(ii) Americium-241 has a half-life of 430 years.
Suggest why the long half-life of americium-241 is important for use in a smoke detector.
(iii) Americium-241 has the nuclide notation \( ^{241}_{95}\text{Am} \).
State the number of neutrons in the nucleus of an atom of americium-241.

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

• Topic P4.3.1 — Circuit diagrams and circuit components (Part (a)(i))
• Topic P4.2.4 — Resistance (Part (a)(ii))
• Topic P5.2.2 — The three types of nuclear emission (Part (b)(i))
• Topic P5.2.4 — Half-life (Part (b)(ii))
• Topic P5.1 — The nucleus (Part (b)(iii))

▶️ Answer/Explanation

(a)(i) Correct symbol for battery and switch; series connections
The circuit diagram should show a battery, a switch, and the doorbell symbol connected in series with wires forming a complete loop.

(a)(ii) V = 4 × 1.5 OR 6.0 (seen); R = V/I (in any form) OR 6(.0)/3(.0); 2.0 (Ω)
Total voltage = 4 × 1.5 = 6.0 V. Using Ohm’s law, R = V/I = 6.0/3.0 = 2.0 Ω.

(b)(i) helium nucleus / 2 protons and 2 neutrons
An α-particle consists of 2 protons and 2 neutrons, which is identical to a helium-4 nucleus. It has a charge of +2e.

(b)(ii) decay rate needs to remain constant
A long half-life means the activity remains reasonably constant over the detector’s lifetime, so it does not need frequent replacement and remains reliable.

(b)(iii) 146
Number of neutrons = mass number – proton number = 241 – 95 = 146.

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.

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