Which of the following surfaces will absorb radiant heat energy?

1. Analyze the question The question asks which surface will absorb radiant heat energy. In JAMB this is usually phrased to mean "which surface is the best absorber," so we compare the colours listed.

2. Explain the concept Radiant heat (thermal radiation) travels as electromagnetic waves, mainly infrared. When it hits a surface, three things can happen:

• Absorbed: converted into heat in the surface
• Reflected: bounced back
• Transmitted: passed through

The colour and texture of a surface decide which of these dominates:

• Dull black surfaces are the best absorbers (and also the best emitters) of radiant heat.
• Shiny, white or light surfaces are poor absorbers because they reflect most of the radiation.

A perfectly black body absorbs all radiation that falls on it. This is the reference ideal in physics.

3. Solution

• A. White: reflects most radiation, so it is a poor absorber.
• B. Red: absorbs some, but reflects red light and is not the best absorber.
• C. Black: absorbs nearly all the radiation falling on it, so it is the best absorber.
• D. Blue: reflects part of the radiation, so it is not as good as black.

4. Answer The surface that absorbs radiant heat energy best is black, which is option C.

5. Exam tip Remember: "Black = Best absorber, Best emitter. White/Shiny = Best reflector." This is why:

• Solar water heater panels are painted black.
• People in hot Nigerian weather prefer white or light clothes, since they reflect heat.
• The inside of a vacuum flask is silvered, to reflect heat back and reduce radiation loss.

Whenever a JAMB question asks about heat absorption, look for "black" or "dull black" among the options.