The questions are on the electromagnetic spectrum test. Take it under real conditions before reading the mark scheme.
Quick answer: The electromagnetic spectrum is a family of transverse waves that travel at 3.0 × 10⁸ m/s in a vacuum. This mark scheme gives the model answers and the marks for the 8 questions of the Physics 9-10 test on electromagnetic spectrum, from order to phones and X-rays, with the equivalent answers to accept.
Model answers with mark allocations follow. Award marks for equivalent wording, and give error carried forward when a wrong earlier value is used correctly in a later calculation.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: HS-PS4-4, HS-PS4-5
Question 1 Order (2 marks)
Gamma rays, X-rays, ultraviolet, visible, infrared, microwaves, radio waves.
Marking: 2 marks for all correct; 1 mark if only one pair is swapped.
Question 2 Radio wavelength (3 marks)
- 3.0 × 10⁸ m/s
- λ = c ÷ f = 3.0 × 10⁸ ÷ 1.20 × 10⁶ = 250 m
Marking: 1 mark for the speed; 1 mark for the equation with values; 1 mark for the answer (the answer mark can be earned only with 3.0 × 10⁸). Total 3 marks.
Question 3 Choosing waves (2 marks)
Infrared: remote control or heater, because objects absorb and emit it as heat. X-rays: medical imaging, because they pass through soft tissue but are absorbed by bone. Any correct use with matching property.
Marking: 1 mark for each use with its property.
Question 4 Ionising radiation (3 marks)
- Radiation with enough energy to remove electrons from atoms, forming ions.
- Ultraviolet (high end), X-rays, gamma rays (any two).
- Cancer, cell damage or mutation (any one).
Marking: 1 mark for each part.
Question 5 Ultraviolet damage (3 marks)
Ultraviolet has a higher frequency than visible light, so its photons carry more energy and can damage skin cells and DNA, causing burns or cancer. The farmer can wear a hat and long sleeves and use sunscreen with a high protection factor.
Marking: 1 mark for higher energy or ionising damage; 1 mark for each correct precaution.
Question 6 Weather radar (2 marks)
Total distance = speed × time = 3.0 × 10⁸ × 4.0 × 10⁻⁵ = 1.2 × 10⁴ m. The pulse goes there and back, so the cloud is 6.0 × 10³ m (6.0 km) away.
Marking: 1 mark for 1.2 × 10⁴ m; 1 mark for halving.
Question 7 Missing regions (2 marks)
- A is microwaves; B is ultraviolet.
- Gamma rays
Marking: 1 mark for both names; 1 mark for gamma rays.
Question 8 Phones and X-rays (3 marks)
Ionising needs each wave to carry enough energy to remove an electron from an atom. The energy carried increases with frequency. Microwaves have a low frequency, so their energy is too small to remove electrons; X-rays have a very high frequency and can.
Marking: 1 mark for the idea of removing electrons; 1 mark for energy depending on frequency; 1 mark for microwaves lower, X-rays higher.
