The photoelectric effect is best demonstrated with which metal, given that it has a very low work function?
Correct answer: A. Caesium
- A. Caesium
- B. Iron
- C. Tungsten
- D. Platinum
Explanation
Caesium's work function is only about 2 eV, so ordinary visible light is enough to eject electrons, whereas tungsten and platinum need ultraviolet. This is why alkali metals are used in photocells and photomultipliers. The low value reflects how loosely the single outer electron of an alkali metal is held.
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About Photons and the Particle Model of Light
The particle model treats light as photons with energy E equals hf and momentum related to wavelength. Questions involve the photoelectric effect, work function, threshold frequency, stopping potential and photon energy, while distinguishing particle behaviour from the wave description of interference and diffraction.
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