Which of the following is the first particle discovered which is believed to be elementary, that is, not made up of further constituents

Appeared in: KPSC Staff Nurse - 2017

Explanation

The electron was discovered in 1897 by J.J. Thomson, making it the first discovered particle among the options.
It is classified as a lepton, which is a type of elementary (or fundamental) particle, meaning it is not composed of smaller particles.
The question asks for the first discovered elementary particle, and the electron fits both criteria.

Option A: The gluon, while an elementary particle, was experimentally confirmed in 1979, much later than the electron.
Option B: The concept of the photon as a particle of light was formalized by Einstein in 1905, which is after the discovery of the electron in 1897.
Option D: The proton is not an elementary particle. It is a composite particle made up of three quarks (two up, one down).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain History of Particle Physics and Elementary Particles as background academic context rather than a clinical decision trigger.
While this is a fundamental physics question, the principles of particle physics are crucial for modern medical technologies.
High-energy photons are the basis of radiation therapy for cancer treatment.
Positron Emission Tomography (PET) scans, a vital diagnostic imaging tool, work on the principle of positron-electron annihilation.

How to Approach the Question

First, understand the two key criteria in the question: 'first discovered' and 'elementary'.
An 'elementary' particle means it cannot be broken down into smaller parts.
Evaluate each option based on these criteria.
Recall that the proton is made of quarks, so it is not elementary. This eliminates the 'Proton' option.
Compare the discovery dates of the remaining elementary particles: Electron (1897), Photon (concept 1905), and Gluon (1979).
The electron has the earliest discovery date, making it the correct answer.

Concept Tested & Keywords

Concept Tested: History of Particle Physics and Elementary Particles
Stem keywords: first particle discovered, elementary, not made up of further constituents
Lead-in keywords: Which
Negative lead-in flag: false

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Practise the full KPSC Staff Nurse - 2017

Attempt every question from this paper in a timed mock, then review the full solution for each one.