Radiant Heat

Radiant Heat

• The Sun's rays heat the Earth.

• ​The space between the Sun and Earth is a vacuum and contains practically no matter.

• This means that thermal energy can't be transferred by conduction or direct contact. It also can't be transferred by convection or the movement of fluids.

​How do we get heat from the sun?

• Radiant thermal energy is similar to visible light because they are both examples of electromagnetic waves.

• But most radiant thermal energy is invisible because it has longer waves than red light. For this reason, it is called infrared radiation.

• All objects radiate thermal energy. We can't see it, but we can often feel it.

​How do we get heat from the sun?

In your books:

The Sun heats the Earth through invisible infrared radiation. Heat can't travel through space by conduction or convection, so it reaches us as radiation. All objects give off thermal energy, even if we can’t see it.

Multiple Choice

Select the option that best completes this sentence.

Radiation is a type of thermal energy transfer:

• By the movement of gases or liquids

• Where one object transfers all of its energy to another object

• Between objects that are touching

• Where energy travels in waves rather than the motion of particles

• I'm not sure

Multiple Choice

Identify whether the following statement is true or false. 

Only the Sun radiates thermal energy. 

• True

• False

• I'm not sure

Multiple Select

Determine which of the following are reasons why thermal energy from the Sun is unable to reach Earth through conduction or convection. 

• The Sun and Earth are not touching

• Particles move too fast in space

• Space is a vacuum with no particles

• Conduction and convection can only happen on Earth

• I'm not sure

Multiple Choice

A pizza is cooking in a wood-fired oven.

Determine which of the following is the best example of radiation. 

• The bricks transfer thermal energy to the pizza dough

• Hot air cooks the toppings on the pizza

• The coals transfer thermal energy to the oven and pizza

• I'm not sure

Categorize

Options (12)

The transfer of energy through the base of the metal pan.

The transfer of energy from the Sun to the ice cream.

The transfer of energy through the air in the hot-air balloon.

The transfer of energy from the Earth’s core to its surface.

The transfer of energy from the hot-water bottle to the bed.

The transfer of energy through the water in the kettle.

The transfer of energy from the cup to the person’s hands.

The transfer of energy from the heater to the person’s hands.

The transfer of energy from the flame to the food in the oven.

The transfer of energy from the soup to the metal spoon.

The transfer of energy from the bonfire to the spectators.

The transfer of energy from the heating element to the bread.

Decide whether the main energy transfer process in each scenario is conduction, convection or radiation.

Conduction

Convection

Radiation

Multiple Choice

The image below was taken with an infrared camera. It shows a man pouring a cup of tea for a woman sitting near a radiator. The scale on the right-hand side shows how the colours represent different temperatures.

Identify the object radiating the most thermal energy. 

• The woman's leg

• The radiator

• The man's head

• The teapot

• I'm not sure

Multiple Choice

Infer from the infrared image what the temperature of the top of the radiator is approximately.

• 20

• 30

• 35

• 45