I’m sure you all have noticed this but never really cared enough to find out why it happens.
When boiling water, why is it when you stick in a metal utensil(spoon) into the boiling water and take it out it has a rainbow pattern on it similar to a soap bubble?
No,I’ve never noticed.
Been dippin’ ma spoon fir years. Never noticed that. No siree.
I’ve seen it, it happens a lot on stainless steel. I think it has a lot to do with heating up the residue that’s left on the spoon, probably dried soap that you didn’t wash off.
I can tell you why the rainbow pattern forms, will that help?
looks around, doesn’t see anyone say “no”
Good. OK, you’ve got a thin, transparent film of some sort: Oil on water, a soap bubble, etc. I’m not sure what sort of film we’re dealing with here (Water? Soap?), but that actually doesn’t matter (much). Now, when light shines on this film, some reflects off the front surface, and some reflects off the back. If the thickness of the film is just right, relative to the wavelength of the light ([sup]1[/sup]/[sub]4[/sub] l, [sup]3[/sup]/[sub]4[/sub] l, [sup]5[/sup]/[sub]4[/sub] l, etc., if it’s in air, like a bubble, or [sup]1[/sup]/[sub]2[/sub] l, l, [sup]3[/sup]/[sub]2[/sub] l, etc, if it’s up against a solid surface, like in this case), then the crests of the waves from the front surface will line up with the crests of the waves reflecting off the back surface, and the reflected light will be reinforced. If you change the thickness of the film by [sup]1[/sup]/[sub]4[/sub] l, then the situation will be reversed, and the crests will line up with the troughs, resulting in partial or total cancellation. This means that if you shine light of many wavelengths (i.e., white) on a film, some colors will be reinforced, and some cancelled, so the reflected light will appear to be a particular color, depending on the thickness. If the thickness of the film varies, as it’s almost sure to, then different regions of it will reflect different colors, and you see a swirly rainbow thing.
Does this help?
Then why do I see a rainbow pattern on the perfectly dry, oilless metal panels enclosing a furnace when they get hot? (Not hot enough to glow, mind you, just kinda ouchy hot.)