Beyond the rainbow

I've blogged before about the small one's love of rainbows, and how we made a spectrum of visible light on the wall with a prism.  On a gloriously sunny morning, the small one noticed a rainbow on our floor.  We had a look at how it was being made, and discovered that the sunlight streaming in through the window was hitting a holographic panel on the baby's playpen, and being both reflected and separated into the spectrum, forming a fuzzy rainbow shape on the carpet.

Rainbow created by the holographic playpen panel

Inspired by this discovery, we had another play with the prism, and 'catching rainbows' on some white paper. We found we could make either short wide spectra or long thin ones depending on how we held the prism.  He pointed out the colours of the rainbow - red, orange, yellow, green, blue, indigo and violet, and ran to get his wooden rainbow to show me that they were in the same order. 

Spectrum (rainbow) on the wall made using daylight and a triangular prism

The wooden rainbow only has six pieces, with a single colour (purple) in place of indigo and violet.  We talked about how purple was a bit like violet, and then I asked whether there was anything beyond violet in the rainbow (spectrum) on the wall.  He thought not, so I asked if there might be something his eyes couldn't see, but maybe other animals could.  He pondered for a minute, and then asked if there was something.  I explained that there was, and it was called ultraviolet.

Telling Mummy about the colours of the rainbow

I asked if there was anything beyond the red at the other end of the rainbow.  He wanted to know if there might be, so I explained that there was infrared.  He looked slightly disbelieving so I told him that I'd find a way for us to be able to see the infrared with a special camera (he loves Maddie Moate's special cameras on her Do You Know programme)...

We have a baby monitor which switches over to using infrared light in the dark.  Later in the day when it was getting a bit darker, we made a little 'darkroom' out of sofa cushions and positioned the baby monitor so it switched over to its nighttime mode.  We also turned the sound off to prevent audio feedback as we had the camera and monitor screen close together.

I remembered that some banknotes are printed in inks which absorb and reflect infrared differently to visible light as a measure to prevent counterfeiting, so I found a banknote and we had a look at it.  I asked him who the lady wearing the crown was, and he said it was Mummy; I'm not sure whether to take this as a complement or be offended, but anyway, I explained that it is the Queen...!  We took a look at the note on the baby monitor camera, and discovered that only half of the Queen is visible.  He was quite impressed by this, and we had a look a few times!

Half the Queen on the baby monitor screen

I reclaimed the cash, and we had a look at his toy pandas.  We have a little one ('baby') which we bought when I traded him down from the enormous one in the shop (which in hindsight was a mistake).  We also have a big one, which was bought on a return visit to the same shop after I made the mistake of accepting that maybe baby panda missed his Daddy.   As it happens, I quite like pandas, so I didn't oppose the acquisition of the large one with much gusto. The pandas have remained popular with the small one for several months and frequently sleep in or around his bed, and hence I knew from seeing them on the monitor in the dark that the black fur fabric of one reflects infrared light and appears white, so the panda doesn't look much like a panda in infrared, but the other still appears black and white.  Neither panda's eyes absorb infrared, but they do absorb visible light so whilst they look black to your eyes, they are white on the infrared camera.  He was intrigued, but also a bit puzzled. He decided he wanted his pandas back and took them away to play.  Later in the day he suggested that we needed to get Mummy panda from the shop too because baby was missing his Mummy.  I don't know whether he's got an experiment in soft toy genetics in mind if baby doesn't look like his Daddy?!

Daddy and baby panda in daylight - their black fur absorbs visible light

Daddy and baby panda seen in infrared - baby panda's black fur doesn't absorb infrared

We were talking a little later on a walk to the shop to encourage his baby brother to sleep about what we'd seen, and he remembered about infrared and how it was beyond red in the rainbow.  He had also remembered about seeing half of the Queen, and wanted to show Daddy at the weekend.  I think we'll come back to the infrared camera as there are some other interesting things we could look at and discuss.