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O Levels Physics (5054)•5054/12/O/N/21
Question 15 from 5054/12/O/N/21

Explanation

Infrared absorption depends on color and surface texture

Steps:

  • Identify that good absorbers of infrared (heat) radiation follow principles similar to visible light: dark colors absorb more than light colors.
  • Recall that shiny (polished) surfaces reflect radiation, reducing absorption, while dull (matt) surfaces trap and absorb more.
  • Apply Kirchhoff's law of thermal radiation: good absorbers are also good emitters, and ideal blackbodies are dark and rough.
  • Match to options: black absorbs, dull enhances absorption by minimizing reflection.

Why A is correct:

  • Black surfaces absorb most infrared radiation, and dull texture prevents reflection, maximizing absorption per Kirchhoff's law.

Why the others are wrong:

  • B: Shiny texture reflects infrared, making it a poor absorber despite black color.
  • C: White reflects infrared, regardless of dull texture.
  • D: White and shiny both promote reflection of infrared.

Final answer: A

Topic: Radiation

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