Infrared radiation means electromagnetic waves with frequencies in a range just lower than for red light.

To emit infrared radiation is to give out infrared radiation.

The temperature of an object measures how hot or cold it is.

A Leslie cube is a hollow metal cube that can be filled with hot water. Each side has a different colour and finish so emits different intensities of infrared radiation.

Emitting infrared radiation

Combined science

In A-level physics, some pupils will build on this knowledge to learn about the photon model of electromagnetic radiation and the use of electromagnetic radiation for collecting evidence about the universe or for generating images of the inside of a human body.

In the Measuring waves unit, pupils learnt about the measurable features of a wave, the relationship between them and the wave equation.

Electromagnetic waves

Physical activity and equipment requiring safe use

A pupil has test tubes of hot water covered in different colours of paper. He investigates whether colour affects the rate of infrared emission. Match each variable with its type in this experiment.

This variable affects the rate of energy transfer.

This variable affects temperature change when energy is transferred.

This reduces energy transfer by evaporation.

A pupil has beakers of hot water covered in different colour paper to investigate how colour affects temperature drop caused by infrared energy transfer. Match the parts of her method with the reason.

One object is shiny and the other is dull.

The objects are also losing heat by conduction.

An infrared thermometer may show different temperature readings for two objects that are at the same temperature. Which of the following is a possible explanation?

sometimes a good and sometimes a poor absorber

Match the following types of surface to the description of how well it absorbs infrared radiation.

If a surface is a good absorber of IR radiation, then it is a good emitter.

If a surface is a good absorber of IR radiation, then it is a poor emitter.

If a surface is a poor absorber of IR radiation, then it is a good emitter.

If a surface is a poor absorber of IR radiation, then it is a poor emitter.

Which of the following statements about the absorption and emission of infrared (IR) radiation are correct?

The radiation emitted by the rod transfers more energy per second.

The wavelength carrying the most energy per second becomes a longer wavelength.

The range of emitted wavelengths increases to include shorter wavelengths.

A metal rod is heated until it glows red. 
Which of the following statements describes what happens if the rod gets hotter?

Which of the following is not a type of electromagnetic radiation?

Which of the following types of electromagnetic radiation are emitted by a hot light bulb?

Surfaces can absorb radiation. Which of the following words or phrases is closest in meaning to the word absorb?

It has higher frequencies than light but lower frequencies than microwaves.

It has lower frequencies than light but higher frequencies than microwaves.

Which of the following statements about infrared radiation are correct?

The maximum displacement of a wave from the rest position.

The number of wavelengths passing a point each second.

A regular, repeating forwards–and–backwards movement.

Distance between two equivalent points on neighbouring wavelengths.

Match up the following key terms about waves with their definitions.

Thermal conduction can happen in a vacuum.

Metals are particularly good thermal conductors.

Thermal conduction in a room starts when warmer air rises.

Thermal conduction happens when energy is transferred by vibrating particles.

Which of the following statements about thermal conduction are correct?

Content guidance

Risk assessment required - equipment

Adult supervision required

Introduction

What will you need for this lesson?

Are you ready to learn?

Equipment

Content guidance

Supervision

Worksheet