Science Burrito has returned after a well-earned holiday. And in the spirit of all good summer holidays, will now bore you with holiday photos. Also, in the spirit of returning to school (which I have now done but all you lucky boys and girls have you whole summer ahead) I shall also give a report on What I Saw on my Summer Holiday.
Ok, I’m hoping that what comes next won’t actually bore you too much. I think it’s really cool, but that might say more about me than anything else. I can’t help but see some real physics happening in the big wide world and getting super excited about it. But you see, or I hope you will see soon, it can be truly beautiful. And we’ll start with one of the most beautiful things physics can throw at us on a daily basis: the Rainbow.
I saw a rainbow on my holidays! I know, I know, who hasn’t right? But here’s something you might not have realised about rainbows. To see a normal rainbow in the sky, you need three things. First you need rain (duh!). Second, you need sun (double duh!) and third, you need to be standing in between the two of them.
Ha! Bet you didn’t realise that one. If you did, well done, you know your rainbows!
The reason you need to be in the middle of the sun and the rain is pretty cool. You may remember this blog, in which we saw an awesome experiment where we saw tonic water fluoresce. In that blog I told you a few things about light. I told you white light is made up of all the colours of the rainbow, and then I showed you this picture:
Now, to look at this picture, you’d think you need the rain to be in the middle:
But that’s a bit misleading, and I apologise for that. When you see a normal rainbow, what actually happens in the light reflects off the inside of the raindrop as it is spreading out and bounces backwards, just like the total internal reflection we saw in the tonic water.
So you need to have the sun behind and to be looking at the rain, which acts as big, colour spreading mirror. If you see a double rainbow, the brightest one is after one reflection, the dimmer one is after two reflections.
But! I wasn’t completely dishonest with you (hooray!) because you can actually see a rainbow without the light bouncing around inside the raindrop. It doesn’t work with rain though, but with very thin misty clouds instead (which I guess is just like stationary rain). Just like the first gif, the light goes through the rain and spreads out into a rainbow. But the cool thing is, you see the whole thing! When you see a rainbow, if the Earth wasn’t in the way, you would see a full circle of colour, and when you see one this way, that’s what you see: a halo of colour around the sun.
I had to take the photo like this, because otherwise the sun would have over exposed my camera. But you can see it’s not bending towards the ground like a normal rainbow, and trust me, when I came out from behind the trees it was a full circle and it was really, really cool.
I also took a photo of this bird (a Little Egret). There is plenty of science behind birds, and maybe one day I will write about them. But, for now, I just wanted to show you a picture of a bird.