Where does this come from, and can I check it?

Weak blue light ejects electrons from a metal that intense red light cannot touch. The figure is taken from Nobel Prize, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a science fact?

Yes. It sits on the Science shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

What else can I read about it?

The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

Mondo Knows Facts

The photoelectric effect needs a minimum frequency

Weak blue light ejects electrons from a metal that intense red light cannot touch Shining light on a metal can knock electrons out of it, but only if each photon carries enough energy. Brightness changes how many electrons leave, while colour decides whether any leave at all. Einstein explained this in 1905 by treating light as packets of energy and won the 1921 Nobel Prize for it. It sits in Mondo's science collection, one of 200 facts that each trace back to the reference below.

Where this comes from

Nobel Prize

Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.

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Science trivia

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Tags: physics, light, quantum

The photoelectric effect needs a minimum frequency: the short answers

Where does this come from, and can I check it?: Weak blue light ejects electrons from a metal that intense red light cannot touch. The figure is taken from Nobel Prize, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a science fact?: Yes. It sits on the Science shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.