page_title: Soap bubble
section_title: Wetting
hierarchical_section_title: Soap bubble / Physics / Wetting
caption_attribution_description: English: A soap bubble wetting a ultrahydrophobic surface
context_page_description: A soap bubble is an extremely thin film of soapy water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact with another object. They are often used for children's enjoyment, but they are also used in artistic performances. Assembling several bubbles results in foam.
  When light shines onto a bubble it appears to change colour. Unlike those seen in a rainbow, which arise from differential refraction, the colours seen in a soap bubble arise from interference of light reflecting off the front and back surfaces of the thin soap film. Depending on the thickness of the film, different colours interfere constructively and destructively.
context_section_description: When a soap bubble is in contact with a solid or a liquid surface wetting is observed. On a solid surface, the contact angle of the bubble depends on the surface energy of the solid., A soap bubble has a larger contact angle on a solid surface displaying ultrahydrophobicity than on a hydrophilic surface – see Wetting. On a liquid surface, the contact angle of the soap bubble depends on its size - smaller bubbles have lower contact angles.
caption: A soap bubble wetting an ultrahydrophobic surface
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