CIE iGCSE Co-Ordinated Science P3.3 Electromagnetic spectrum Exam Style Questions Paper 1
▶️ Answer/Explanation
Television remote controls use infrared (IR) radiation to send coded pulses of electromagnetic radiation to the TV’s receiver — IR has a wavelength just longer than visible red light and is safe at low intensities.
Gamma rays and X-rays are ionising radiation (dangerous), while ultraviolet is used in sterilisation and banknote checking — none of these are used in TV remotes.
✅ Answer: (B)
Gamma rays and X-rays are ionising radiation (dangerous), while ultraviolet is used in sterilisation and banknote checking — none of these are used in TV remotes.
✅ Answer: (B)
▶️ Answer/Explanation
The electromagnetic spectrum, from lowest to highest frequency, runs: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.
Checking option B: microwaves come before infrared, and infrared comes before gamma-rays, so this sequence is correctly increasing in frequency.
✅ Answer: (B)
Checking option B: microwaves come before infrared, and infrared comes before gamma-rays, so this sequence is correctly increasing in frequency.
✅ Answer: (B)
▶️ Answer/Explanation
The spectrum in order of increasing frequency is: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma.
Gamma radiation has a higher frequency than visible light, not lower, so A is wrong; ultraviolet has a smaller wavelength than microwaves, so C is wrong; X-rays have a smaller wavelength than visible light, so D is wrong.
Infrared sits above radio waves in the frequency order, so infrared correctly has a higher frequency than radio waves.
✅ Answer: (B)
Gamma radiation has a higher frequency than visible light, not lower, so A is wrong; ultraviolet has a smaller wavelength than microwaves, so C is wrong; X-rays have a smaller wavelength than visible light, so D is wrong.
Infrared sits above radio waves in the frequency order, so infrared correctly has a higher frequency than radio waves.
✅ Answer: (B)
Question
Which electromagnetic waves have the lowest frequency?
(A) gamma
(B) infrared
(C) ultraviolet
(D) radio
▶️Answer/Explanation
Ans: D
Question
Which part of the electromagnetic spectrum is involved in thermal energy transfer by radiation?
A. infrared
B. radio
C. ultraviolet
D. X-rays
▶️Answer/Explanation
Answer: A. infrared
Explanation: Infrared radiation is responsible for thermal energy transfer by radiation. It is emitted by hot objects and can be absorbed by other objects, causing them to heat up.