Question

which of the following is not an example of radiation? warming up some leftovers in the microwave. coffee remaining hot in an insulated mug after many hours in spite of the outside temperature being cooler than the coffee. sunburn after sunbathing all day on the beach. getting an x-ray to see if a bone is broken after falling off the monkey bars.

Explanation:

To determine which is not radiation, recall: Radiation is energy transfer via electromagnetic waves (e.g., sun’s UV, X - rays, microwaves).

• Warming leftovers in a microwave: Microwaves (radiation) heat food.
• Sunburn: UV radiation from the sun.
• X - ray: Ionizing radiation.
• Coffee in an insulated mug: Insulation reduces conduction/convection (heat transfer via contact/movement of fluids), not radiation. So this is heat retention via reduced heat loss (not radiation).

Answer:

Coffee remaining hot in an insulated mug after many hours in spite of the outside temperature being cooler than the coffee.