InfraRed Radiation Bell Work InfraRed Radiation Bell Work

Infra-Red Radiation

Bell Work – Infra-Red Radiation

Bell Work - Answer Infra-red radiation is heat radiation. It is part of the electromagnetic spectrum and is a type of wave.

Agree Learning Outcomes l l l Know that all objects emit and absorb infrared radiation. (knowledge) Understand that the hotter an object is the more infrared radiation it radiates in a given time. (comprehension) Know that dark, matt surfaces are good absorbers and good emitters of infrared radiation. (knowledge) Try an experiment to show light, shiny surfaces are poor absorbers and poor emitters of infrared radiation. (apply) Complete exam style questions to display knowledge (apply)

Prepare to Learn

Present New Information - What are infra red waves? How does this heat energy travel from the Sun to the Earth? The Earth is warmed by heat energy from the Sun. ? infrared waves There are no particles between the Sun and the Earth, so the heat cannot travel by conduction or by convection. The heat travels to Earth by infrared waves. These are similar to light waves and are able to travel through empty space.

Present New Information - What are infrared waves? Heat can move by travelling as infrared waves. These are electromagnetic waves, like light waves, but with a longer wavelength. This means that infrared waves act like light waves: l They can travel through a vacuum. l They travel at the same speed as light – 300, 000 m/s. l They can be reflected and absorbed. Infrared waves heat objects that absorb them and are also known as thermal radiation.

Demo – Leslies Cube

Copy this table into your books Tin Colour Shiny Black Start temperature inside Start temperature outside Temp after 5 mins inside mins outside

Construct – Do all surfaces emit the same amount of radiation? l You will be conducting an experiment similar to the demo you have just watched showing how surfaces vary the amount of thermal radiation. Follow the instructions on the task sheet. Warning! The tins used may get very hot!

Emitting thermal radiation All objects emit (give out) some thermal radiation. Certain surfaces are better at emitting thermal radiation than others. worst emitter best emitter matt black white silver Matt black surfaces are the best emitters of radiation. Shiny surfaces are the worst emitters of radiation. Which type of kettle would cool down faster: a black kettle or a shiny metallic kettle?

Mini Review – Do you agree that we have met the below green objectives? l l l Know that all objects emit and absorb infrared radiation. (knowledge) Understand that the hotter an object is the more infrared radiation it radiates in a given time. (comprehension) Know that dark, matt surfaces are good absorbers and good emitters of infrared radiation. (knowledge) Try an experiment to show light, shiny surfaces are poor absorbers and poor emitters of infrared radiation. (apply) Complete exam style questions to apply knowledge (apply)

Demo – Do all surfaces absorb the same amount of thermal radiation?

Absorbing thermal radiation Infrared waves heat objects that absorb (take in) them. Certain surfaces are better at absorbing thermal radiation than others. Good emitters are also good absorbers. worst emitter best emitter matt black best absorber white silver worst absorber Matt black surfaces are the best absorbers of radiation. Shiny surfaces are the worst emitters because they reflect most of the radiation away.

Apply Knowledge 1– Think Pair Share l Why are solar panels used for heating water covered in a black layer? l Think! l Pair! – 30 s l Share!

Mini Review

Apply Knowledge 2 l Answer the exam style questions

How did you do? a) A matt black surface is a very good absorber of infrared compared to light, shiny surfaces. (2 marks) b) Shiny metal. Shiny surfaces are poor emitters of infrared. Matt black surfaces are good emitters of infrared. (2 marks) How many did you get out of 4? What did you get wrong? Why? Don’t forget to use a different coloured pen to correct your answers as you go!

Mini Review – You should now know all of the below objectives l l l Know that all objects emit and absorb infrared radiation. (knowledge) Understand that the hotter an object is the more infrared radiation it radiates in a given time. (comprehension) Know that dark, matt surfaces are good absorbers and good emitters of infrared radiation. (knowledge) Try an experiment to show light, shiny surfaces are poor absorbers and poor emitters of infrared radiation. (apply) Complete exam style questions to display knowledge (apply)

Review – Take time to reflect on the lesson Fill in at least 3 statements on the learning log l What I learned today was… l What I found interesting about the work was…. l What surprised me was… l The skills I used today were ……. l I want to know more about …… l Right now I am feeling ……. . l You could help me by ……. .