Physical World Chapter 1 Class 11 Physics NCERT Textbook PDF

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Physical World

Chapter 1: Physical World

1.1 What is Physics?

Humans have always been curious about the world around them. The night sky with its bright celestial objects has fascinated humans since time immemorial.

The regular repetitions of the day and night, the annual cycle of seasons, the eclipses, the tides, the volcanoes, and the rainbow have always been a source of wonder.

The world has an astonishing variety of materials and a bewildering diversity of life and behavior.
The inquiring and imaginative human mind has responded to the wonder and awe of nature in different ways.

One kind of response from the earliest times has been to observe the physical environment carefully, look for any meaningful patterns and relations in natural phenomena, and build and use new tools to interact with nature.

This human endeavour led, in course of time, to modern science and technology The word Science originates from the Latin verb Scientia meaning ‘to know.

The Sanskrit word Vijñãn and the Arabic word Ilm convey similar meanings, namely ‘knowledge’. Science, in a broad sense, is as old as the human species.

The early civilizations of Egypt, India, China, Greece, Mesopotamia, and many others made vital contributions to its progress.

From the sixteenth century onwards, great strides were made in science in Europe.

By the middle of the twentieth century, science had become a truly international enterprise, with many cultures and countries contributing to its rapid growth.

What is Science and what is the so-called Scientific Method? Science is a systematic attempt to understand natural phenomena in as much detail and depth as possible, and use the knowledge so gained to predict, modify and control phenomena.

Science is exploring, experimenting, and predicting what we see around us. The curiosity to learn about the world, and unraveling the secrets of nature is the first step toward the discovery of science.

The scientific method involves several interconnected steps: Systematic observations, controlled experiments, qualitative and quantitative reasoning, mathematical modeling, prediction, and verification or falsification of theories.

Speculation and conjecture also has a place in science; but ultimately, a scientific theory, to be acceptable, must be verified by relevant observations or experiments.

There is much philosophical debate about the nature and method of science that we need not discuss here.

The interplay of theory and observation (or experiment) is basic to the progress of science.
Science is ever dynamic.

There is no ‘final’ theory in science and no unquestioned authority among scientists.

As observations improve in detail and precision or experiments yield new results, theories must account for them, if necessary, by introducing modifications.

Sometimes the modifications may not be drastic and may lie within the framework of existing

For example, when Johannes Kepler (1571-1630) examined the extensive data on
planetary motion collected by Tycho Brahe (1546-1601), the planetary circular orbits in heliocentric theory (sun at the center of the solar system) imagined by Nicolas Copernicus (1473–1543) had to be replaced by elliptical orbits to fit the data better.

Language English
No. of Pages15
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NCERT Solutions Class 11 Physics Chapter 1 Physical World

1.1 Some of the most profound statements on the nature of science have come from Albert Einstein, one of the greatest scientists of all time. What do you think did Einstein mean when he said: “The most incomprehensible thing about the world is that it is comprehensible”?


The complex physical world involves different orders of magnitudes in space, time, and mass. Despite this, nearly all physical phenomena can be expressed in terms of a few basic laws. By this view, Einstein’s statement “The most incomprehensible thing about the world is that it is comprehensible” becomes very clear.

1.2 “Every great physical theory starts as a heresy and ends as a dogma”. Give some examples from the history of the science of the validity of this incisive remark.

One of the general observations in our daily life is that light travels in a straight line. When Huygens propounded his wave theory, it was a heresy.

However, soon it became dogma as interference patterns, refraction, etc. could be successfully explained on the basis of wave theory.

It was believed that light was only energy but when the photoelectric effect was discovered it was proposed that light had a particle nature too, this was greatly debated and treated as heresy. However, Einstein finally proved it with his quantum theory of light. Henceforth, it has been treated as a dogma.

1.3 “Politics is the art of the possible”. Similarly, “Science is the art of the soluble”. Explain this beautiful aphorism on the nature and practice of science


Politicians make anything and everything possible to win votes. Science is a systematized study of observation.

Scientists and researchers study these observations and then work out certain laws from them. There is a multitude of natural phenomena taking place in this universe and all of them can be explained in terms of some basic laws. For e.g. F = mg is true for you and me and also for a star.

Thus, in science we see that various phenomena are related, they are soluble and can be explained with similar or the same law. This goes on to justify that science is the art of the soluble just as politics is the art of the possible.

1.4 Though India now has a large base in science and technology, which is fast expanding, it is still a long way from realizing its potential of becoming a world leader in science. Name some important factors, in your view have hindered the advancement of science in India.

Here are some important factors that have obstructed the growth of science in India:

  • Lack of infrastructure and funds for quality research work in science.• Poor pay scales and other facilities for scientists as compared to administrators.
  • Science education is neither properly oriented nor directed. It needs specific directions depending on our requirements. Industrialists are the actual consumers of new technology and research. The industrialists of this country have little confidence in the ability of Indian scientists. There is practically no coordination between the researchers and the industrialists.
  • Rural-based science education is nearly non-existent so the majority of the population is deprived of the benefits of advancements in technology and science.

1.5 No physicist has ever “seen” an electron. Yet, all physicists believe in the existence of electrons. An intelligent but superstitious man advances this analogy to argue that ‘ghosts’ exist even though no one has ‘seen’ one. How will you refute his argument?


Even though an electron has never been ‘seen’ but its effects have been observed and its practical evidence has been tested and proved.

E.g. electricity.

However, regarding spirits and ghosts, even though there are many claims and sightings, standardized scientific reading and evidence have never been observed or successfully tested. Thus, we really cannot state with a cent percent surety that they exist.

Physical World Textbook With Solutions PDF Free Download

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