IDUSCIENCE L08 Radiation

Radiation

Objectives

• Recall that heat can travel by radiation

• Explain how infrared radiation is similar to light

• Describe some ways of using infrared radiation

• Compare certain colours’ ability to retain heat energy

Keywords

reflect/reflection

emit/emission

absorb/absorption

colour

vacuum

infrared radiation

Introduction

•There is nothing but empty space (a vacuum)
between the Sun and the Earth, so heat
can’t travel to the Earth by conduction or
convection.

Multiple Choice

By which process is thermal energy transferred through a vacuum?

• conduction only

• convection only

• conduction and convection only

• radiation only

Infrared radiation

•All the heat we get from the Sun travels as
radiation (sometimes called infrared
radiation)
•IR Radiation is similar to light because

•It does not need anything (a medium) to travel
through
•It can go through transparent substances (like
glass, air, water)

Multiple Choice

What is the main source of radiation on Earth?

• Mars

• Sun

• Saturn

• Moon

Radiation

• All hot things emit (give out) infrared radiation.

• When radiation hits something it can be absorbed
  (taken into the object) or
  reflected (bounce away from the object)

Multiple Choice

Which of the following materials expands the most when heated?

• gas

• plasma

• liquid

• solid

Example

The fire is radiating heat.

The campers stay warm because they are absorbing the heat

Thermal images

• Instruments that create pictures of heat rather than light.

• They measure infrared radiation and convert the data into map of temperatures.

Hottest parts are white

and red and cooler

parts are yellow, green

and blue.

Thermal images

The police and fire service use
infra-red cameras to find people in
the dark.

Infra-red has no colour, but a
computer can put a false colour on the
camera image so we can ‘see’ the
object.

The colours are put on a scale which
corresponds to temperature. White,
yellow and red usually represent the
warmest areas; green, blue and black
usually represent the coolest.

Year 7 Science

Multiple Choice

We feel the intense heat from the Sun when we stand in the open during noon time. How is heat transferred from the Sun to the Earth?

• By radiation only.

• By conduction and radiation only.

• By convection and radiation only.

• By conduction, convection and radiation.

Multiple Choice

What is the unit of measurement for thermal energy?

• Calorie

• Joule

• Watt

• Volt

Multiple Choice

How does heat transfer occur in liquids and gases?

• Heat transfer in liquids and gases occurs through friction.

• Heat transfer in liquids and gases occurs through conduction.

• Heat transfer in liquids and gases occurs through radiation.

• Heat transfer in liquids and gases occurs through convection.

Multiple Choice

How does heat transfer occur in solids?

• Convection

• Radiation

• Evaporation

• Conduction

Interpret data

•You will need to interpret data from two
experiments in your worksheets

Experiment 1

Experiment 2

5 differently coloured iron blocks were
left out in the sun. The time it took for the sun to heat the iron block was measured.

5 differently coloured metal cups were
filled with hot water. The water was 100°C. After 5 minutes the temperature of water was measured to determine how much heat was lost.