The bonfire from the opening image has a lot of thermal energy. Thermal energy is the total kinetic energy of moving particles of matter, and the transfer of thermal energy is called heat. Thermal energy from the bonfire is transferred to the hands by thermal radiation. Thermal radiation is the transfer of thermal energy by waves that can travel through air or even through empty space, as shown in the Figure 1.1. When the waves of thermal energy reach objects, they transfer the energy to the objects, causing them to warm up. This is how the fire warms the hands of someone sitting near the bonfire. This is also how the suns energy reaches Earth and heats its surface. Without the energy radiated from the sun, Earth would be too cold to support life as we know it. Thermal radiation is one of three ways that thermal energy can be transferred. The other two ways are conduction and convection, both of which need matter to transfer energy. Radiation is the only way of transferring thermal energy that doesnt require matter.

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## questions

thermal energy is the total kinetic energy of moving particles of matter.

``````-->  a. true

b. false
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examples of thermal radiation include thermal energy traveling through

``````a) the air from a campfire to you.

b) empty space from the sun to earth.

c) a metal pan to water inside the pan.

-->  d) two of the above
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no matter is required to transfer thermal energy by

``````a) conduction.

b) convection.

d) two of the above
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only very hot objects radiate thermal energy.

``````a. true

-->  b. false
``````

life on earth depends on thermal energy radiated from the sun.

``````-->  a. true

b. false
``````

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