Transfer Of Thermal Energy - Radiation Quiz

Dark surfaces are better absorbers of infrared radiation compared to light or shiny surfaces. Dark animal fur will absorb more infrared radiation than a shiny metal tray, a white plastic bag, or writing paper, which either reflect or absorb less radiation. The dark color of the fur allows it to absorb a larger amount of heat from infrared radiation, making it the best absorber among the options provided.

The panels of a solar heater are painted black to improve absorption of infra-red radiation. Black surfaces have a higher absorption rate for radiation compared to other colors, allowing the panels to absorb more of the Sun's energy and convert it into heat. This helps to maximize the efficiency of the solar heater in converting sunlight into thermal energy for heating water.

When a copper plate is heated to 100oC and then allowed to cool, it cools by emitting infra-red radiation. Infra-red radiation is a form of electromagnetic radiation with longer wavelengths than visible light. As the copper plate cools, the atoms and molecules in the plate lose energy and emit this radiation. This radiation carries away the excess heat energy from the plate, causing it to cool down.

Black and dull surfaces are the best absorbers and emitters of infra-red radiation because they have a higher ability to absorb and emit radiation compared to other surfaces. Black surfaces absorb more radiation because they have a higher absorption coefficient, meaning they can absorb a larger amount of radiation that falls on them. Dull surfaces, on the other hand, have a higher emissivity, which allows them to emit a larger amount of radiation. This combination of high absorption and high emission makes black and dull surfaces the best absorbers and emitters of infra-red radiation.

Thermal energy reaches the wax through a combination of radiation and conduction. The electric heater emits infrared radiation, which directly heats the surface of the metal plate. This heat is then conducted through the metal, transferring thermal energy from the hotter areas near the heater to the cooler areas where the wax is located. As the wax absorbs this heat through conduction, it eventually melts, causing the cork to drop off.

The thermal energy from a campfire reaches the scouts' faces primarily through radiation. Radiation is the transfer of energy through electromagnetic waves, such as infrared radiation, which does not require a medium like air to transfer heat. While convection might play a role in moving warm air around, the direct warmth felt by the scouts from the campfire is due to radiation, as air is a poor conductor of thermal energy.

Aluminium is a good reflector of thermal energy. When the hand comes in contact with the aluminium, the thermal energy radiated by the hand is reflected back towards the hand instead of being absorbed by the aluminium. This reflection of thermal energy causes the hand to feel warm.

In metal hot-water pipes, thermal energy is primarily transferred through the metal via conduction. Conduction is the process where heat is transferred through a material by direct contact of its particles. Once the heat is conducted through the metal pipes, it is then transferred to the air in the room primarily by convection. Convection involves the movement of warm air rising and cooler air sinking, which circulates the heat throughout the room.

he fact that container P has a lower temperature after an hour indicates that it has transferred heat more effectively than container Q. This suggests that container P is a better conductor of heat, meaning it allows heat to flow through it more readily, resulting in the hot water inside losing heat faster. In contrast, container Q, which retained more heat, is likely a poorer conductor (or a better insulator) than container P.

A vacuum will prevent heat transfer by conduction and convection only because there are no particles or molecules present in a vacuum to transfer heat through direct contact or through the movement of fluids. However, a vacuum does not prevent heat transfer by radiation, as radiation can occur through the emission and absorption of electromagnetic waves, which do not require a medium to travel through.