infrared radiation

the theory is that

the hotter an object the more it will emit rather than absorb to cool down and vice versa

some objects absorb more than others

the lesile cube

has 4 surfaces shiny metallic white shiny black matt black

first step

fill cube with boiling water make sure all sides are same temp throughout

control v

set infrred detector same distance from each surface

to make the experiment repeatable

do multiple goes

you should find

black surfaces detect more ir more than white and matt more than shiny

you can also do this

with two surfaces getting heated with a infrared heater and see which surface has enough energy absorbed to transfer to a bit of wax to melt