Recall

What is emissivity?

• The ability of a material to absorb heat

• The ratio of radiation emitted by a surface to the radiation emitted by a perfect black body at the same temperature

• The reflection of heat by a surface

• The ability of a material to conduct heat

Which of the following is true about a perfect black body?

• It reflects all incident radiation.

• Its emissivity is 0.

• It absorbs and emits radiation at all wavelengths.

• It emits no radiation.

Which of the following factors does NOT affect the emissivity of a material?

• Surface roughness

• Material type

• Temperature

• The material’s thickness

How does surface roughness affect emissivity?

• A rough surface usually has higher emissivity than a smooth surface.

• A smooth surface always has higher emissivity than a rough surface.

• Surface roughness has no effect on emissivity.

• Roughness increases the reflectivity of the material.

What was the material of the Disk used in the experiment?

• Copper

• Aluminum

• Iron

• Steel