Question

Which of the following is not a fundamental particle? (a) Electron (b) Proton (c) Neutron (d) X-rays

Short answer

X-rays are not a fundamental particle because they are electromagnetic radiation, not a particle.

Step-by-step solution

Understanding Fundamental Particles

Fundamental particles, also known as elementary particles, are particles that are not composed of smaller particles. They are the basic building blocks of matter and cannot be broken down into anything more simple.

Analyzing the Options

Examine each option to determine if it is a fundamental particle or not. Electrons are fundamental particles as they are elementary and cannot be divided into smaller parts. Protons and neutrons, on the other hand, are made up of quarks, therefore they are not fundamental. They are part of a category called composite particles. X-rays are not particles at all; they are a form of electromagnetic radiation.

Identifying the Non-Fundamental Particle

Given the above information, eliminate the options that are known to be fundamental or not applicable. The electron is a fundamental particle, while protons and neutrons are not. Since x-rays aren't particles, they are the odd one out compared to the rest of the options.

Key concepts

Elementary Particles

Elementary particles, often referred to as fundamental particles, are the smallest building blocks of the universe. These are the indivisible components that all matter is made from. Unlike atoms which consist of a nucleus surrounded by electrons, elementary particles are not composed of any smaller particles. They form part of the standard model of particle physics which includes particles like electrons, quarks, and neutrinos.

Electrons are a classic example of an elementary particle. They possess a negative electric charge and are found in all atoms, orbiting the nucleus. In the context of our exercise, electrons can't be further divided into smaller parts, which is why they embody the definition of an elementary particle. Knowing this, students understand why option (a) cannot be the correct choice.

Composite Particles

In contrast to elementary particles, composite particles are made up of two or more elementary particles bound together. The most common examples in the nucleus of atoms are protons and neutrons, collectively known as nucleons. Protons and neutrons themselves consist of quarks, which are held together by the strong force via gluons.

• Protons are made of two 'up' quarks and one 'down' quark.
• Neutrons consist of one 'up' quark and two 'down' quarks.

These particles demonstrate the concept of subatomic structures within themselves, thereby making them non-fundamental or composite. Hence, for the given exercise, both proton (b) and neutron (c) would be classified as 'not a fundamental particle' due to their quark composition.

Electromagnetic Radiation

Electromagnetic radiation is a form of energy that is all around us and takes many forms, such as radio waves, microwaves, X-rays, and gamma rays. Unlike particles, which have mass, electromagnetic waves are massless and travel at the speed of light in a vacuum. These waves are characterized by their wavelength and frequency.

X-rays are a type of electromagnetic radiation commonly used in medical imaging to view the inside of the body. Importing knowledge from physics helps clarify why option (d) X-rays, is indeed 'not a fundamental particle'. Since electromagnetic radiation is not considered to be made of particles at all, but rather energy transmitted through waves, X-rays can't be grouped with particles. Therefore, it's clear that (d) stands out from the other options as being entirely different in nature and is the correct answer to the exercise.