Heat is radiated by hot objects in the form?

Analyze the question: The question asks about the form in which heat is radiated by hot objects. This is about thermal radiation, one of the three methods of heat transfer (conduction, convection and radiation).

Explain the concept: Radiation is heat transfer by electromagnetic waves, and it needs no material medium. That is why the Sun's heat reaches us through the vacuum of space. Hot objects emit electromagnetic radiation, and the type depends on temperature:

• Moderately hot objects (a hot iron, a stove, the human body) emit mostly infrared radiation, which we feel as heat.
• Very hot objects (a glowing filament, the Sun) also emit visible light, but a large share of their heat is still carried by infrared.
• X-rays come from very high-energy processes, such as electrons striking a metal target in an X-ray tube. They are not the way ordinary hot objects radiate heat.

Step-by-step solution:

1. Heat radiation travels as electromagnetic waves.
2. Option A (x-rays): these are far too energetic for ordinary hot objects. Eliminate.
3. Option B (light energy): only very hot objects glow visibly, and most hot objects (a hot pot, a warm iron) give off heat without any visible light. Not the general answer.
4. Option D (solar energy): this is energy from the Sun, a source rather than a form of radiation. Eliminate.
5. Option C (infrared rays): this is the radiation that carries heat from hot bodies. Correct.

Answer: C. Infrared rays.

Tip: Think "infrared = heat rays". Whenever a question asks what carries radiant heat, the answer is infrared. Remember that thermal radiation is part of the electromagnetic spectrum and needs no medium.