WHAT IS PHYSICS
INTRODUCTION
Almighty Allah created this universe billions of years ago with a single word "be" and at once it came into being. He inducted several principles and laws in it to sustain its function. Now from the day of their creation every particle of the universe is following these laws. These laws are known as "THE LAWS OF NATURE". Apparently they are hidden from the eyes of mankind and are mysteries for him. Our solar system including our earth is a small component of this immense universe. This is composed of matter and hence is a physical world.
Human being is the best creature of Allah in this world and has been endowed with many qualities. One of them is to unfold and discover the Laws of Nature. He has curiosity in his nature. When he looks around, he observes that innumerable number of events are taking place. He sees that clouds are floating in the sky rainfalls from them. Thunder occurs and lightening flashes in the clouds. Several tiny plants and beautiful grass appear on the surface of dry land. He observes that there are many objects that catch fire while others do not. Heat burns things and destroys their identity. Some matter appears in solid state, some in liquid and other in gaseous state. These and many other observations raise several questions in his mind. He asks where and how clouds are formed. How lightening flashes in the clouds? Why some objects catch fire and others do not? What is the nature of heat? How is it produced? How matter appears in different states? Such and many similar questions excite him to find the answers of these questions.Physics a branch of science which helps him to get the answers of his queries.
The word "Physics" comes from a Greek word "Physikos" meaning “natural." Now it is defined as a science which deals with the interaction of matter and energy The physicists have divided the subject of physics into various branches; each branch has acquired a title of a full subject nowadays. Main branches of physics are given below:
1. Mechanics: It deals with the motion of objects with or without reference force.
2. Electricity: It is concerned with the phenomena and effects related electric charges.
3. Electromagnetism: It deals with observations, principles, laws and methods that relate electricity and magnetism.
4. Solid-State physics: It is concerned with the structure and properties of solid materials.
5. Atomic physics: It is concerned with the structure and properties of the atom.
6. Nuclear physics: This branch is concerned with the structure, properties and reactions of the nuclei of atoms.
7. Plasma physics: It is concerned with the properties of highly ionized atoms forming a mixture of bare nuclei (nuclei without electrons) and electrons
8. Bio-physics: It is concerned with the application of physical methods and explanation to bio-physical systems and structures.
9. Astro physics: It is concerned with the study of the physics of astronomical bodies
In addition to these branches also there are other branches, say low temperature physics, particle physics, optics, etc.
IMPORTANCE OF PHYSICS IN DAILY LIFE:
In our daily life we use many things as a routine. But we seldom think how they are made. We use several electric appliances in our homes. For example, electric fan, electric bulb, refrigerator, airconditioner, juicer, grinder, etc. They all use electric power. We use buses, cars, railway carriages, aeroplanes etc., for long distances. All of these are run by engines. Engines of these vehicles are manufactured on the principles of thermodynamics. We listen to radio programmes. We see the events far away from us on the television screen and enjoy various programmes telecast from the T.V. station. In all electronic devices and appliances solid state physics plays a vital role. Laser technology is widely used in defence system, metallurgy, medical science & astronomy which has its roots in atomic physics. Many countries including Pakistan, utilize nuclear energy to produce electric power. Production of nuclear energy is the area of nuclear physics.
We can see that in every walk of life physics is involved in one way or the other. Thus physics is playing a vital role in framing our life style and influencing our way of thinking.
In a scientific work the most important thing is observation. Observations are taken very carefully and systematically. In this way all possible informations are gathered about a physical phenomenon under investigation. Keeping these observations in mind a scientist makes some hypothesis or postulate to explain the phenomen.on. A hypothesis is a notion of a scientist on which he tries to explain the phenomenon. He designs a theory on the basis of hypothesis and gives an elaborated explanation about the phenomer.on. The theory is checked by experiments. If theoretical and experimental results agree with each other, the theory is regarded correct otherwise it is discarded. This is one way of investigation of a problem in physics, Some times a scientist presents a theory on the basis of rational reasoning and predicts some phenomena to take place under certain conditions. Experiments are designed to test this theory. Again if predicted results are obtained, the theory is supposed to be correct and then this theory becomes a law. The law is such a statement regarding the behaviour of nature which explains the observations and experiments of the past and can predict about other aspects of nature.
Newton made a hypothesis about the nature of light. According to him light consists of extremely small particles moving with a very high velocity. He named these particles as corpuscles. Based on this hypothesis he developed a theory, called corpuscular theury of light, which could explain the phenomenon of reflection and refraction of light and the formation of shadows which were experimental facts. Thus theory was accepted because it could explain a few properties of light as mentioned above. According to corpuscular theory of light, light travels faster in a denser medium (water) than rarer medium (air) whereas, according to wave theory light travels faster in rarer medium than a denser medium. The phenomena of interference, diffraction and polarization of light can not be explain on the basis of corpuscular theory of light. These phenomena can be explained successfully with help of wave theory of light. Foucault determined speed of light in water experimentally which showed that light
travels slower in water than air. This result was against the corpuscular theory of light hence the theory was discarded and wave theory was accepted. Later on phenomena of photo electric effect and compton effect were observed which could not be explained with the help of wave theory of light. Einstein presented another theory regarding the nature of light which is known as quantum theory of light. According to this theory light has dual nature; some times it behaves like a wave and some times like a particle. It consists of packets of energy, called photons. All the phenomena regarding the nature of light are explained with the help of the quantum theory of light.
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