Question: what is your favourite experiment you ever carried out?

Eleanor Holmes answered on 12 Nov 2013:

My favourite experiment that I have ever carried out takes me right back to 2nd year of school.

I was 13 or so and I had just had a double science class where we talked about the primary colours of light. I had learned that the primary colours of light (red, blue, green) were different to the primary colours of ink (cyan, magenta, yellow) but that they behaved in a similar way. i.e. Add together red, green and blue at the same intensities and you will get white light. Add together just two of the primary colours and you get the secondary colours of light (which are, pleasingly, cyan, magenta and yellow). Our teacher had read to us from the book which explained that if you mixed Red and Blue light you got Magenta light. Mix Green and Blue and you get Cyan light.

I put up my hand and asked if the pattern continued, if you mix Red and Green light, do you get Yellow? My teacher (who was not a good scientist) stared at me for a moment in confusion, then advised me to just stick to what the book said for the exam.

Well. I went straight home and got out three torches from our cupboard under the stairs. I used some sweet wrappers in Red, Green and Blue to create coloured torches and I went into a room with a big white wall and turned off the lights and saw for myself that Red and Green light shone together make Yellow light!

On that day I became a scientist.