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CIE iGCSE Co-Ordinated Science P2.3.3 Radiation Exam Style Questions Paper 2

CIE iGCSE Co-Ordinated Science Paper 2 - All Chapters

Question

Which surface is the best absorber of thermal radiation?

A. dull black
B. dull white
C. shiny black
D. shiny white

▶️ Answer/Explanation
Dull black surfaces are the best absorbers (and emitters) of thermal radiation. Shiny surfaces reflect radiation, and white surfaces reflect more than black. Dull black has the highest absorptivity.
✅ Answer: (A)

Question

Which row shows the colour of outer clothing that helps to keep the wearer cool on a hot, sunny day and the reason why this colour is effective?

▶️ Answer/Explanation
To keep cool on a hot, sunny day, clothing should be white because white surfaces are poor absorbers (and good reflectors) of radiation from the Sun. This means less thermal energy is absorbed by the clothing, keeping the wearer cooler. Black surfaces are good absorbers and would absorb more radiation, making the wearer hotter. Therefore, option D is correct: white clothing is effective because it is a bad absorber of radiation from the Sun.
✅ Answer: (D)

Question

Which statement about thermal radiation is correct?

A. A dull surface is a good absorber and a good reflector of thermal radiation.
B. A dull surface is a poor absorber and a poor reflector of thermal radiation.
C. A shiny surface is a good absorber but a poor reflector of thermal radiation.
D. A shiny surface is a poor absorber but a good reflector of thermal radiation.

▶️ Answer/Explanation
A dull surface absorbs thermal radiation well but reflects it poorly, since \(\text{absorption} + \text{reflection}\) cannot both be maximal at once.
A shiny surface reflects most incoming radiation, meaning it is a poor absorber but a good reflector, matching statement D.
✅ Answer: (D)

Question

Two methods of cooking are grilling under a red-hot heater and frying in a shallow metal pan.

How does thermal energy pass through the air to reach the food in method 1 and how does thermal energy pass through the bottom of the metal pan in method 2?

▶️ Answer/Explanation
In grilling, thermal energy travels through the air from the red-hot heater to the food by infrared radiation, since air is a poor conductor.
In frying, thermal energy passes through the solid metal pan by conduction, as vibrating particles pass energy to neighbouring particles.
✅ Answer: (C)

Question

Which method of thermal energy transfer occurs in a vacuum and which region of the electromagnetic spectrum is mainly involved in this type of thermal energy transfer?

▶️ Answer/Explanation
Thermal radiation is the only method of heat transfer that can occur through a vacuum, as it doesn’t require a medium. It is primarily in the infrared region of the electromagnetic spectrum. Convection requires a fluid medium, so it cannot occur in a vacuum.
✅ Answer: (C)
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