Required Pratical(Infrared radiation)

What is the aim of experiment

To see how much infrared radiation is absorbed or radiated by surface depending on material

What is the independent variables in this experiment

-Colour of cube

What’s the dependent variable

temperature of cube

What are the control variables

-Same amount of hot water

-Same starting temperature of water

-Same time intervals

-Distance between Leslie cube and infrared detector

What’s a Leslie’s cube

A metal cube what helps us see how much infrared is emitted from different surfaces

What are the 4 different surfaces of a Leslie cube

-Shiny metallic surface

-White surface

-Shiny black surface

-Matt black surface(not shiny)

Describe the experiment

1)Place an empty Leslie cube in a heat proof mat

2)Fill Leslie cube with hot water from kettle

3)Hold a thermometer against each of four vertical faces if cube to see if they’re same temperature

4)Point an infrared detector at each of the four surfaces at a set distance of 10cm and record the amount of infrared emitted

5)Make sure to keep the same distance between the Leslie cube and infrared detector so measurements are repeatable

6)Do it more than once to see if results are repeatable.

What should be the results of the expedient

-Matt black surface emits most infrared

-Then shiny black

-Then white

-Then shiny metallic

What should you use if you don’t have a detector and why is it a problem

-You should use a thermometer with bulb painted black

-However resolution is less than detector so we may not able to to detect the large differences between the surfaces using a thermometer whereas detector is more likely to detect differences

How do we measure the absorbance of radiation from difference surfaces

1)Get a infrared heater and on either side put 2 metal plates

2)One plate is painted with shiny metallic paint

3)Other is painted with Matt black paint

4)On outside of plate we use Vaseline to attach a drawing pin

5)Switch on heater and start timing

6)The temperature of metal plates increases as they absorb infrared

7)We record the time it asked for Vaseline to melt and the drawing line to fall off

8)We find out drawing pin falls off the Matt black plate first as Matt black surface absorb more infrared than shiny metallic surfaces

What can we conclude about Matt black surfaces from both experiments

It’s much better at emitting and absorbing infrared than shiny metallic surfaces

-In fact infrared red is reflected from shiny metallic surfaces

What are the safety precautions for experiments

-Make sure to not touch hot water as you may burn yourself- run under cold water if so

-Do not overfill kettle

-Keep water from eletrical equipment

-Carry out experiment while standing to react to spilling

-Don’t move cube when it’s full of boiling water