A Soap Bubble Is Thinner Than a Wavelength of Light
A bubble is a thin film of liquid enclosing gas. Its colours come from the film being thinner than light itself.
A bubble is a thin film of liquid surrounding gas. The swirling colours have nothing to do with the soap: the film is only a few hundred nanometres thick, thinner than the wavelengths of visible light, so light reflecting off the front and back surfaces interferes with itself. As the film thins before bursting, the colours shift and then vanish.
- A gas pocket in liquid. *A soap bubble.*
- An unsustainable rise in prices. *A housing bubble.*
- A protected space. *In a bubble.*
- To boil gently. *The stew bubbled.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | bubble | A single bubble. |
| Plural | bubbles | Rising bubbles. |
| Verb | bubble | It bubbled over. |
| Adjective | bubbly | A bubbly texture. |
| Related | foam | Sea foam. |
How it is used in a sentence
- The bubble burst in 2008.Economics.
- He lives in a bubble.Cut off from wider reality.
- Bubbles are spherical because that shape minimises surface area.Physics.
Famous economic bubbles
- Tulip mania — Dutch tulip bulb prices in the 1630s
- South Sea Bubble — British share speculation in 1720
- Railway mania — Britain in the 1840s
- Dot-com bubble — internet shares around 2000
- Housing bubble — property prices before the 2008 crash
Of imitative origin, first recorded in the fourteenth century. The financial sense dates from the South Sea Bubble of 1720.
Why are bubbles round?
Surface tension pulls the film into the shape with the least surface area for the volume of gas, which is a sphere.
Why do bubbles show colours?
Light reflecting from the front and back of an extremely thin film interferes with itself, reinforcing some colours and cancelling others.