An object absorbs 12 W and emits 12 W. Radiation is its only energy transfer. Its heat capacity is fixed, no phase change occurs, and only its thermal energy store can change. What happens to its temperature?

• It stays steady because the energy rates match
• It rises because absorbed energy keeps arriving
• It falls because emitted energy keeps leaving

Which statement usually describes matt black paint compared with polished metal at the same temperature?

• It absorbs infrared well but emits very little
• It absorbs and emits infrared well
• It reflects most infrared and emits very little

Mara says the energy in sunlight reaches Earth by conduction. Is this statement true?

Circle one:   True   False

Earth and its atmosphere initially have balanced energy input and output. Increased greenhouse absorption then reduces energy escaping to space. Absorbed sunlight stays unchanged. What is the expected long-term response?

• Cooling until still less thermal radiation escapes from the system
• No change because unchanged sunlight prevents any energy imbalance
• Warming until outgoing radiation again balances absorbed sunlight

Two cans start at the same temperature above the same uniform surroundings. Heat capacities, exposed areas and radiation exposure match. Only radiation transfers energy and only thermal stores change, with no phase change. Why does the matt black can initially cool faster than the polished can?

• Its paint reduces the water's heat capacity despite the stated match
• Its surface gives a greater net radiative loss in these conditions
• Its paint stops infrared absorption while keeping emission unchanged

An object's temperature rises while its surface area and emissivity stay unchanged. What happens to its total emitted thermal power?

• It decreases as kelvin temperature increases
• It stays constant despite the temperature rise
• It increases with the fourth power of kelvin temperature

An object emits 12 W and absorbs 8 W, with no other transfers. Its heat capacity is fixed. Only its thermal energy store changes; no phase change occurs. Lee says absorption keeps its temperature steady. Which explanation checks this claim?

• It cools because its net energy loss is 4 W
• It warms because its net energy gain is 4 W
• It stays steady because absorption never stops

Two cans have equal fixed heat capacities and initial temperatures. Only thermal energy stores change; no phase changes occur. The black can absorbs 7 W and the polished can absorbs 3 W. Each loses 2 W in total, with no other inputs. Which initially warms faster?

• The polished can, with a net energy gain of 5 W
• The black can, with a net energy gain of 5 W
• Both cans equally, with net energy gains of 2 W