how and when protons were discovered if they are not visible to eyes
The discovery of protons, along with other subatomic particles, was a significant development in the field of atomic and nuclear physics. Protons were not directly observed with the naked eye but were discovered through a series of experiments and the development of atomic and nuclear models. Here's a brief history of the discovery of protons!
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Late 19th Century: The understanding of atomic and subatomic particles began to take shape in the late 19th century with the work of scientists like J.J. Thomson and Ernest Rutherford.
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Thomson's Discovery of the Electron (1897): J.J. Thomson conducted experiments with cathode rays and discovered the existence of negatively charged particles, which he called "electrons." This discovery laid the groundwork for understanding atomic structure.
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Rutherford's Gold Foil Experiment (1909): Ernest Rutherford conducted the famous gold foil experiment, which involved firing alpha particles at a thin gold foil. To his surprise, some alpha particles were deflected backward, indicating the presence of a small, dense, positively charged nucleus at the center of an atom. This nucleus was later identified as containing protons.
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Discovery of Protons (Early 20th Century): Based on Rutherford's findings, scientists proposed the existence of positively charged particles in the nucleus of an atom. In 1911, Rutherford himself hypothesized the presence of "protons" to account for the positive charge in the nucleus.
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Confirmation of Protons (1919): The term "proton" was formally introduced by Rutherford in 1919. Protons were identified as positively charged subatomic particles within the nucleus of an atom.
Protons were indirectly discovered through the study of atomic and nuclear behavior, especially in experiments involving radioactivity, particle emissions, and the behavior of alpha and beta particles. The understanding of atomic and subatomic particles continued to evolve with the development of quantum mechanics and the Standard Model of particle physics in the 20th century.