The existence of positron was discovered in the:
Correct answer: B. Cosmic radiation
- A. Thermal radiation
- B. Cosmic radiation
- C. Electromagnetic radiation
- D. Non-electromagnetic radiation
Explanation
An experiment on Cosmic rays performed by Carl D Anderson led to the accidental discovery of the positron. Anderson allowed cosmic rays to pass through a cloud chamber and a lead plate. A magnet surrounded this apparatus, caused the particles to bend in different directions based on their electric charge. The ion trail left by each positron appeared on the photographic plate with a curvature matching the mass-to-charge ratio of an electron, but in a direction that showed its charge was positive. It was the first evidence of anti-matter.
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Classical physics cannot explain blackbody radiation and related observations, leading to Planck’s quantum theory, in which energy is emitted or absorbed in discrete packets. Photons provide the particle model of light, with energy and momentum linked to frequency and wavelength, including the photoelectric effect and its threshold frequency.
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