Branches of Physics

 

Branches of Physics

The physical universe has many moving parts and is not simply what is observed through the naked eye. Physics is also how the most prominent objects interact with the smallest and everything in between. Since physics is such a broad subject, it has to be broken into smaller categories or disciplines, also known as fields of study.

There are three main categories of modern physical study:

1. Classical physics covers electromagnetism, classical mechanics, thermodynamics, and statistical mechanics. Classic physics provides action and reaction, showing how objects acting in a system will interact with other objects in that same system.
2. Relativity has two types of study; there is general and specific relativity. General relativity deals with how the law of gravity interacts with objects; this has a significant bearing in astrophysics and astronomy. Special relativity concerns how objects interact in a vacuum or are devoid of gravity.
3. Quantum physics is the most recent course of study in physics. Here, scientists study quantum mechanics, quantum statistics, quantum electrodynamics, and quantum field theory. This branch deals primarily with objects at an atomic and subatomic level. It answers questions like, "what makes a proton different from a neutron?"

Mechanics

The study of mechanics is both broad and specific. Broadly, mechanics study objects, their motion, energy, and how they interact with other objects and energy. There are two sub-branches of mechanics, quantum mechanics and classical mechanics.

• Quantum mechanics, studies how atom and subatomic particles act and react with one another; similar to how the atom is held together, what happens if two atoms collide? What makes up the atomic particles; how and why do two atoms bond; what holds together millions of atoms into a complex compound?
• Classical mechanics follows the same principles as quantum, at a much larger scale. Examples of classical mechanics would be predicting planetary orbits or the path of a bullet, black holes, friction between a car tire and the road, why water has surface tension, or the arc of a baseball as it is thrown across home plate.

Mechanics can explain a minor interaction, like why an electron is attracted to a proton, and the most significant interaction, like why the earth orbits the sun.

Optics

One of our two most important senses is that of sight. In physics, the study of light and its properties is called optics.

One reason light is a fascinating study subject is that it contains the properties of a wave and particles. Additionally, electromagnetic waves make up light, meaning it has properties of electricity and magnetism and does not need a medium to move.

There are several different types of light:

• Visible
• Ultraviolet
• Infrared
• X-ray
• Radio Waves
• Gamma Rays

 

Various Branches of Physics

Physics can be classified into various branches, but classical physics is mainly concerned with energy and matter. The traditional branches of classical physics are Optics, Acoustics, Electromagnetics, and Classical mechanics. With the rapid development of physics, the scope of the subject is growing so large that it is not possible to cover physics under the above branches. A number of main branches of physics are discussed below.

Mechanics

Mechanics is the branch of physics that deals with the motion of an object without or with the reference of force. Mechanics can be further divided into two branches, namely quantum mechanics and classical mechanics. Quantum mechanics deals with the behaviour of the smallest particles like neutrons, protons, and electrons, while classical mechanics is the branch that deals with laws of motion of forces and physical objects.

Optics

This branch of physics deals with the behaviour, propagation, and properties of light. Optics can be simply described as the study of the behaviour of infrared light, visible light, and ultraviolet.

Thermodynamics

Thermodynamics deals with the study of heat and its relation with work and energy. Thermodynamics also deals with the transmission of heat energy by means of convection, conduction, and radiation.

Electromagnetism

Electromagnetism deals with the study of electromagnetic force like electric fields, light, magnetic fields, etc. There are two aspects of electromagnetism which are “electricity” and “magnetism”.

Relativity

This branch of physics deals with the theorem that was formulated by Albert Einstein. The theory of relativity states that space and time are relative and all the motion must be relative to a frame of reference.

Acoustic

Acoustics deals with the study of sound and its transmission, production, and effects. Acoustics mainly involves the mechanical waves in gases, liquids, and solids, which include vibration, sound, ultrasound, and infrasound.

What is physics?

                                                             What is physics?

 What Matter Means in Physics

By 

Andrew Zimmerman Jones

Andrew Zimmerman Jones

Math and Physics Expert

• M.S., Mathematics Education, Indiana University
• B.A., Physics, Wabash College

Andrew Zimmerman Jones is a science writer, educator, and researcher. He is the co-author of "String Theory for Dummies."

Learn about our Editorial Process

Updated on May 06, 2019

Matter has many definitions, but the most common is that it is any substance which has mass and occupies space. All physical objects are composed of matter, in the form of atoms, which are in turn composed of protons, neutrons, and electrons.

The idea that matter consisted of building blocks or particles originated with the Greek philosophers Democritus (470-380 BC) and Leucippus (490 BC).

Examples of Matter (and What Isn't Matter)

Matter is built from atoms. The most basic atom, the isotope of hydrogen known as protium, is a single proton. So, although subatomic particles aren't always considered forms of matter by some scientists, you could consider Protium to be the exception. Some people consider electrons and neutrons to also be forms of matter. Otherwise, any substance built of atoms consists of matter. Examples include:

• Atoms (hydrogen, helium, californium, uranium)
• Molecules (water, ozone, nitrogen gas, sucrose)
• Ions (Ca2+, SO42-)
• Polymers and Macromolecules (cellulose, chitin, proteins, DNA)
• Mixtures (oil and water, salt and sand, air)
• Complex Forms (a chair, a planet, a ball)

While protons, neutrons, and electrons are the building blocks of atoms, these particles are themselves based on fermions. Quarks and leptons typically aren't considered forms of matter, although they do fit certain definitions of the term. At most levels, it's simplest to state simply that matter consists of atoms.

Antimatter is still matter, although the particles annihilate ordinary matter when they contact each other. Antimatter exists naturally on Earth, although in extremely small quantities.

Then, there are things that either have no mass or at least have no rest mass. Things that are not matter include:

• Light
• Sound
• Heat
• Thoughts
• Dreams
• Emotions

Photons have no mass, so they are an example of something in physics that is not comprised of matter. They are also not considered "objects" in the traditional sense, as they cannot exist in a stationary state.

Phases of Matter

Matter can exist in various phases: solid, liquid, gas, or plasma. Most substances can transition between these phases based on the amount of heat the material absorbs (or loses). There are additional states or phases of matter, including Bose-Einstein condensates, fermionic condensates, and quark-gluon plasma.

Matter Versus Mass

Note that while matter has mass, and massive objects contain matter, the two terms are not exactly synonymous, at least in physics. Matter is not conserved, while mass is conserved in closed systems. According to the theory of special relativity, matter in a closed system may disappear. Mass, on the other hand, may never have been created nor destroyed, although it can be converted into energy. The sum of mass and energy remains constant in a closed system.

In physics, one way to distinguish between mass and matter is to define matter as a substance consisting of particles that exhibit rest mass. Even so, in physics and chemistry, matter exhibits wave-particle duality, so it has properties of both waves and particles.

Visible Light Spectrum

The visible light spectrum is the section of the electromagnetic radiation spectrum that is visible to the human eye. Essentially, that equates to the colors the human eye can see. It ranges in wavelength from approximately 400 nanometers (4 x 10 -7 m, which is violet) to 700 nm (7 x 10-7 m, which is red).1 It is also known as the optical spectrum of light or the spectrum of white light.

Wavelength and Color Spectrum Chart

The wavelength of light, which is related to frequency and energy, determines the color perceived by the human eye. The ranges of these different colors are listed in the table below. Some sources vary these ranges pretty drastically, and their boundaries are somewhat approximate, as they effectively blend into each other. Additionally, the edges of the visible light spectrum blend into the ultraviolet and infrared levels of radiation.

How White Light Is Split Into a Rainbow

Most light that we interact with is in the form of white light, which contains many or all of these wavelength ranges. Shining white light through a prism causes the wavelengths to bend at slightly different angles due to optical refraction. The resulting light is split across the visible color spectrum.

This is what causes a rainbow, with airborne water particles acting as the refractive medium. The order of wavelengths can be remembered by the mnemonic "Roy G Biv" for red, orange, yellow, green, blue, indigo (the blue/violet border), and violet. If you look closely at a rainbow or spectrum, you might notice that cyan also appears between green and blue. Most people cannot distinguish indigo from blue or violet, so many color charts omit it.

By using special sources, refractors, and filters, you can get a narrow band of about 10 nanometers in wavelength that is considered monochromatic light.2 Lasers are special because they are the most consistent source of narrowly monochromatic light that we can achieve. Colors consisting of a single wavelength are called spectral colors or pure colors.

Colors Beyond the Visible Spectrum

The human eye and brain can distinguish many more colors than those of the spectrum. For example, purple and magenta are the brain's way of bridging the gap between red and violet. Unsaturated colors such as pink and aqua are also distinguishable, as well as brown and tan.

However, some animals have a different visible range, often extending into the infrared range (wavelength greater than 700 nanometers) or ultraviolet (wavelength less than 380 nanometers).3 For example, bees can see ultraviolet light, which is used by flowers to attract pollinators. Birds can also see ultraviolet light and have markings that are visible under a black (ultraviolet) light. Among humans, there is variation between how far into red and violet the eye can see. Most animals that can see ultraviolet can't see infrared.

The Visible Light Spectrum
Color	Wavelength (nm)
Red	625 - 740
Orange	590 - 625
Yellow	565 - 590
Green	520 - 565
Cyan	500 - 520
Blue	435 - 500
Violet	380 - 435

 

What Is Time?

Time is familiar to everyone, yet it's hard to define and understand. Science, philosophy, religion, and the arts have different definitions of time, but the system of measuring it is relatively consistent.

Clocks are based on seconds, minutes, and hours. While the basis for these units has changed throughout history, they trace their roots back to ancient Sumeria (Sumer, an area that is now southern Iraq). The modern international unit of time, the second, is defined by the electronic transition of the cesium atom. But what, exactly, is time?

What is time, exactly? Physicists define time as the progression of events from the past to the present into the future. Basically, if a system is unchanging, it is timeless. Time can be considered to be the fourth dimension of reality, used to describe events in three-dimensional space. It is not something we can see, touch, or taste, but we can measure its passage.

Physics equations work equally well whether time is moving forward into the future (positive time) or backward into the past (negative time.) However, time in the natural world has one direction, called the arrow of time. The question of why time is irreversible is one of the biggest unresolved questions in science.

One explanation is that the natural world follows the laws of thermodynamics. The second law of thermodynamics states that within an isolated system, the entropy of the system remains constant or increases. If the universe is considered to be an isolated system, its entropy (degree of disorder) can never decrease. In other words, the universe cannot return to exactly the same state in which it was at an earlier point. Time cannot move backward.

Newton's first law of motion

 

Newton's first law of motion

What is Newton's first law of motion?

Newton's first law of motion states an object at rest or in motion will remain at rest or in motion unless acted upon by an unbalanced force. A ball will continue to move in the forward direction unless an unbalanced force acts on it.

What are the 3 laws of motion?

Newtons's first law of motion states an object at rest or in motion will remain at rest or in motion unless acted upon by an unbalanced force. Newton's second law of motion states the net force (F_{net}) of an object is dependent on both the mass (m) and acceleration (a) of an object. Newton's third law of motion states for every action, there is an equal and opposite reaction.

What are examples of Newton's 1st law of motion?

According to Newton's first law of motion; if a pan full of water was carried around a track, the water would tend to remain traveling forward. However, as the water moves to the left, the water will appear to splash to the right. Space is almost a perfect vacuum void of matter and gravity. Consider a satellite orbiting Earth at 17,500 mph. If a rock were released from the satellite, the rock would orbit earth at a velocity of 17,500 mph next to the satellite.

In 1687 English scientist Sir Isaac Newton published his three laws of motion. Newton's laws of motion are relatively simple statements that revolutionized humanity's understanding of the physical world. Today they are considered foundational to classical mechanics, one of the main branches of physics.

A simple definition of Newton's first law of motion is that it is a law of physics that states that an object at rest or in motion will remain at rest or in motion unless acted upon by an unbalanced force. A force is a push or pull on an object with mass that causes a change in the object's motion. Force is measured in Newtons (N) or kg m/s^{2}.

Balanced Force

The image below shows forces directly acting on the box. Since the magnitude of the arrows are equal, the upward and downward forces are balanced. Balanced forces are equal in magnitude and opposite direction. According to Newton's first law, balanced forces are responsible for keeping an object at rest or maintaining an object's constant velocity.

Inertia is directly proportional to mass. The greater the mass an object has the more the object will resist a change in motion. The elephants in this image have different masses. If these elephants were running at the same speed and had to stop immediately, the more massive elephants would resist changes to their forward state of motion more than the less massive elephants. Thus, according to Newton's first law of motion, the more massive elephants are said to have greater inertia.