Comparing with the same object painted in silvery, object painted in BLACK absorbs heat (a) and emits heat (b). *
A (a): slower ; (b): slower
B (a): faster ; (b): slower
C (a): faster ; (b): faster
D (a): slower ; (b): faster
The correct answer and explanation is :
Correct Answer: C — (a): faster ; (b): faster
Explanation:
When comparing how different surfaces absorb and emit heat, color and surface texture play crucial roles due to their impact on thermal radiation. Black and silvery (or shiny) surfaces have significantly different thermal properties.
1. Heat Absorption:
Black surfaces absorb more heat than silvery or reflective surfaces. This is because black objects absorb all wavelengths of light and convert them into heat, whereas shiny or silvery surfaces reflect most of the incoming radiation. This principle is why black cars feel hotter in the sun than silver ones, and why solar panels are often black — to maximize heat or energy absorption.
2. Heat Emission:
The ability of an object to emit heat is called emissivity. Black objects also emit heat more efficiently than shiny ones. A black surface has a high emissivity (close to 1), meaning it emits thermal radiation well. In contrast, a silvery or reflective surface has a low emissivity (closer to 0), so it retains heat rather than emitting it. That’s why thermal flasks or space blankets often have shiny inner linings — to minimize heat loss by radiation.
Conclusion:
A black-painted object absorbs heat faster because it takes in more radiant energy. It also emits heat faster because it radiates thermal energy more efficiently. In contrast, a silvery-painted object does both more slowly due to high reflectivity and low emissivity.
Thus, Option C is the correct choice:
- (a): faster – black absorbs heat quickly.
- (b): faster – black also emits heat more rapidly.