# GSEB Solutions Class 11 Physics Chapter 1 Physical World

Gujarat Board GSEB Textbook Solutions Class 11 Physics Chapter 1 Physical World Textbook Questions and Answers.

## Gujarat Board Textbook Solutions Class 11 Physics Chapter 1 Physical World

### GSEB Class 11 Physics Physical World Text Book Questions and Answers

Question 1.
Some of the most profound statements on the nature of science have come from Albert Einstein, one of the greatest scientist 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.’’
Answer:
The whole of the physical world around us is very complex in nature because of the occurrence of millions of phenomena. The biological world has its own complexities. So the world seems incomprehensible i.e. as if it cannot be understood. Moreover, we come across wide ranges of mass, length and time which surprisingly be understood and expressed in terms of few basic laws.

In other words, the complex nature of the physical world from atomic to astronomical ranges can be understood in terms of a few basic concepts, so the physical world becomes comprehensible. When viewed in this context, Einstein’s admiration becomes very clear. Not only the motion of planets and satellite can be understood on the basis of Newton’s laws of gravitation, but these laws are applicable throughout the universe.

Question 2.
“Every great physical theory starts as a heresy and ends as a dogma”. Give some examples from the history of science of the validity of this incisive remark?
Answer:
Dogma is an established opinion which is questioned by only a few. It is an authoritative belief. But heresy is anything against the established belief and theory which causes a few ripples in the mind of the intelligent i.e. heresy is an option contrary to the conventional belief. It is true that every great physical theory starts as a heresy and ends as a dogma.

For example:
1. Thomas Young’s wave theory of light started as a heresy and finally ended as “dogma’ when Einstein and other replaced it by quantum theory of light.

2. In ancient times, Ptolemy postulated that earth is stationary and all the heavenly bodies like sun, stars, planets etc. revolve around it. Later, an Italian scientist Galileo postulated that sun is stationary and earth alongwith other planets is revolving around the sun. Galileo was punished by the then authorities for spreading wrong concepts. But later on Newton and Kepler supported Galileo’s theory and now it is a dogma.

3. There was an heresy that inertia of a body depends upon its energy. Einstein put forth a single equation relating mass and energy which is called as mass-energy equivalence relation
(E = mc2) and this is a dogma in Physics.

Question 3.
“Politics is the art of possible”. Similarly, “Science is the art of soluble.” Explain this beautiful aphorism on the nature and practice of science?
Answer:
Nothing is impossible in politics and the politics is the art of possible. It is a well known fact that to win over votes, politicians make anything and everything possible even when they are least sure of the same. In politics, ministry may change overnight, but in science universal laws do not change overnight. Science is a systematised study of observations.

A scientist patiently analyses these observations and comes out with certain laws. e.g. Tycho Brahe worked for twenty long years to make observations on planetary motions. J.Kepler formulated his three famous laws of planetary motion from this huge reservoir of observations.

Thus the statement that science is the art of the soluble means that a wide variety of physical processes are understood in terms of only a few basic concepts i.e. there appears to be unity in diversity as if widely different phenomena are soluble and can be explained in terms of only a few fundamental laws.

Newton’s laws of gravitation are applicable throughout the universe. They are same for two small bodies as well as for the solar system. Whole of the universe can be dissolved into certain laws i.e. we can study the universe on the basis of a few laws.

Question 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 for becoming a world leader in science. Name some important factors, which in your view have hindered the advancement of science in India?
Answer:
Following are some of the important factors which have hindered India’s march towards becoming a world leader in science, and technology:

1. One of the main factors is that the young scientists and technologists are denied the academic freedom which is so necessary for making advances in science and technology.

2. The management of science education in our country is bureaucratic. There is an excess of administrative and political interference in the field of research and technology.

3. There is practically no co-ordination between the researchers and the industrialists who are the actual consumers of new, research and technology. Indian industrialists have little confidence in the ability of Indian scientists and they prefer to import technology from advanced countries (like U.S.A., Japan etc.).

4. The infrastructure for science education in schools and colleges in India is highly in poor state.

5. Science education is neither properly oriented nor directed It needs specific direction depending on our requirements.

6. Sufficient funds are not available for science and technology.

7. There is a lack of employment opportunities for science educated students in our country, thus it takes them away from science and technology.

8. ‘Brain drain’ is another important factor that has hindered India’s progress in science and technology. It leads to a large scale migration of scientists, doctors and technologists.

Question 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?
Answer:
The existence of an electron is a fact though nobody has ever seen an electron because many phenomena have been actually observed in our daily life which depend upon the existence of an electron. On the other hand, ghosts are also not seen but there is not a single phenomenon which can explain the existence of ghosts and there is no phenomenon which can be explained on the basis of the existence of ghosts. Hence clearly, the comparison between the two cases is meaningless.

Question 6.
The shells of crabs found around a particular coastal location in Japan seem mostly to resemble the legendary face of a Samurai. Given below are two explanations of this observed fact. Which of these strikes you as a scientific explanation?
(a) A tragic sea accident several centuries ago drowned a young Samurai. As a tribute to his bravery, nature through its incrutable ways immortalized his face by imprinting it on to the crab shells in ……………………….
(b) After the sea tragedy, fisherman in that area in a gesture of honour to their dead hero, let free any crab shell caught by them which accidentally had a shape resembling the face of a Samurai. Consequently, the particular shape of the crab shell survived longer and therefore, in course of time the shape was genetically propagated. This is an example of evolution by artificial selection.
(Note: This interesting illustration taken from Carl Sagan’s “The Cosmos” highlights the fact that often strange and inexplicable facts which on the first sight appear ‘supernatural’ actually turn out to have simple scientific explanations. Try to think out other examples of this kind.)
Answer:
(b) After the sea tragedy, fisherman in that area in a gesture of honour to their dead hero, let free any crab shell caught by them which accidentally had a shape resembling the face of a Samurai. Consequently, the particular shape of the crab shell survived longer and therefore, in course of time the shape was genetically propagated. This is an example of evolution by artificial selection.

Question 7.
The Industrial Revolution in England and Western Europe more than two centuries ago was triggered by some key scientific and technological advances. What were these advances?
Answer:
The following are the key scientific and technological outstanding contributions that triggered industrial revolution in England and Western Europe during that period i.e. from 1750 A.D. to 1870 A.D:

• Steam engine formed on the application of heat and thermodynamics. British inventor, James Watt in 1769 A.D. invented it and it made possible setting of industries in interior of country, far away from river bank. Machines were then driven by steam power.
• Blast furnace which converts low grade iron into steel cheaply.
• Cotton gin or spinning genny which separates the seeds from cotton three hundred times faster than by the hand.
• Discovery of electricity helped in designing dynamos and motors.
• Discovery ofexplosives not only helped army but also mineral exploration.
• Study of motion and making guns/canons was led by the study of gravitation.
• Invention of powerloom which used steampower was used for spinning and weaving.
• Safety lamp which was used safely in rpines.

Question 8.
It is often said that the world is witnessing now a second Industrial revolution which will transform the society as radically as did the first. List some key contemporary areas of science and technology which are responsible for this revolution?
Answer:
The following are the key areas which will transform radically the present society:

1. Development of superconducting materials at room temperature which will be used in supercomputers and making very powerful electromagnets and transmission , of electric power without any loss of electrical energy.

2. Development of infrared detectors used in night vision, medical surveyallence, remote sensing, geological survey etc.

3. Agriculture is the fundamental area which will transform the village life all over the world.

4. There is a magic revolution in the field of information technology which includes internet, electronic media, superfast computers, satellite communications.

5. Progress in biotechnology and genetic engineering which may totally change the face of the world in coming years.

6. The use of satellites for multiple purpose, possibility of life on other plants etc. are another critically important revolutions brought by space science.

7. Discovery of “Laser” will bring a revolution as Laser beam can be used to transmit thousands of T.V. programmes simultaneously. Ground control of rockets and satellites is possible by laser beams.

8. Laser can also be used in three dimensional photography, bloodless surgery, eye tumors etc.

Question 9.
Write in about 1000 words a fiction piece based on your speculation on the science and technology of the twenty second century?
Answer:
Let us imagine a spaceship moving towards a distant star, 500 light years away. Let it be propelled by current fed into the electric motor consisting of superconducting wires. In space, suppose there is a particular region which has such a high temperature that destroys the superconducting property of electric wires of the motor. At this stage, another spaceship filled with matter and anti-matter comes to the rescue of the first ship and it (i.e. 1st ship) continues its onward journey.

Another way to put is:
Now matter can be changed into energy and energy into matter. A man of 22nd century stands on a plateform of a specially designed machine which energises him and his body disappears in the form of energy. After split of a second, he appears at a place much far away from the previous one just intact.

Question 10.
Attempt to formulate your ‘moral’ vie’ s on the practice of science. Imagine yourself stumbling upon a discovery, which has a great academic interest but is certain to have nothing but dangerous consequences for the human society. How, if at all, will you resolve your dilemma?
Answer:
A scientist aims at truth. A scientific discovery reveals a truth of nature. Thus, any discovery good or bad for human society must be made public, although moral and ethical values may have a conflict with the practice of science. A discovery which appears dangerous today may become useful to mankind sometimes later. We must build up a strong public opinion in order to prevent the misuse of scientific technology. Thus scientists in fact should take up two roles:

• To discover truth and make it public.
• To prevent its misuse, e.g, cloning of animals like sheep ‘Dolly’ is applied to mankind then it will be against ethical values as it will require no man-woman for recreation.

But as a scientific truth it is made public. If 1 stumble on such a thing as a scientist, I will least bother about moral and keep on the truth to become public.

Question 11.
Science, like any knowledge, can be put to good or bad use, depending on the user. Given below are some of the applications of science. Formulate your views on whether the particular application is good, bad or something that cannot be so clearly categorized?

1. Mass vaccination against small pox to curb and finally eradicate this disease from the population. (This has already been successfully done in India)
2. Television for eradication of illiteracy and for mass communication for news and ideas.
3. Prenatal sex determination.
4. Computers for increase in work efficiency.
5. Putting artificial satellites around the earth.
6. Development of nuclear weapons.
7. Development of new and powerful techniques of chemical and biological warfare.
8. Purification of water for drinking.
9. Plastic surgery.
10. Cloning.

Answer:

1. Good
2. Good
3. Bad
4. Good
5. Good
6. Bad
7. Bad
8. Good
9. Good
10. Something which cannot be so clearly categorized

Question 12.
India has had a long and unbroken tradition of great scholarship-in mathematics, astronomy, linguistics, logic and ethics. Yet, in parallel with this, several superstitious and obscurantistic attitudes and practices flourished in our society and unfortunately continue even today-among many educated people too. How will you use your knowledge of science to develop strategies to counter these attitudes?
Answer:
In India, illogical practices and superstitious attitudes have a complex and long origin that are deeply routed in the society and there is no shortcut way to eradicate them. Some of the factors that give birth to these practices are:

1. Caste system.
2. Urge to rule others by keeping them ignorant.
3. Denying of education to larger sections of the society.
4. Self interest of ruling and landlord classes.
5. Lack of scientific knowledge to the people.

To counter these attitudes, the advances in science and technology are to be used to educate people at mass scale which can be done by using electronic mass media like radio, T.V., newspaper and science exhibitions.

Parents are to be encouraged to send their wards to schools for education. This can be developed by developing euriousity among them to know more about the things around them; making them not to believe in superstitions and false beliefs. Top priority is to be given by science to devise a method to control the population explosion of our country, thus the people will have a faith in scientific process and techniques.

Question 13.
Though the law gives women equal status in India, many people hold unscientific views on a woman’s innate nature, capacity and intelligence, and in practice give them a secondary status and role. Demolish this view using scientific arguments, and by quoting examples of great women in science and other spheres and persuade yourself and others that, given equal opportunity, women are on par with men?
Answer:
The nature had made a little difference in the anatomy and feelings of man and woman. There is no difference in the capacity of the woman in:

1. Decision making
2. owning responsibility
3. work and
4. intelligence, it is biological fact that the development of human brain does not depend upon the sex but on the nutrition contents and heredity.

She is endowed with fore-bearence and withstanding stress as additional qualities as compared to man. Hence she is more suitable for administrative and public relation work. She has a persuasive power that makes her an excellent teacher. The exam results of various boards, universities and public exams indicate that girls always excel boys which is a clear scientific evidence that woman is not inferior to man in any sphere of activity like, sports, scaling of mountains as Himalaya or treatment of patients as being a doctor.

We can quote examples of successful women in science and other spheres. The names of Madam Curie, Sarojini Naidu, Mrs. Indira Gandhi, Mrs. Benazir Bhutto, Mrs. Bhandarnaik, Mother Teresa, Margret Thacher, Lata Mangeshker drawn from field vaiying from science to management and Rani Jhansi as the warrior queen are very well known to the world who proved to be far superior than men.

Hence we can say that scientifically women are on par with men. Moreover the nutrition content of pre-natal and post-natal diet contributes a lot towards the development of human mind. If equal opportunities are given to bom men and women, then the female mind will be as efficient as male mind.

Question 14.
“It is more important to have beauty in the equation of physics than to have them agree with experiments.” The great British physicist P.A.M. Dirac held this view. Criticize this statement. Look out for some equations and results in this book which strike you as beautiful?
Answer:
Dirac’s view that, “It is more important to have beauty in the equation of physics than to have agree with experiments” is correct. The equation must be simple and short but must represent whole concept and hence it is beautiful. There is no contradiction in the given statement. An equation of Physics which agrees with experiment must necessarily be both simple and hence beautiful.

The equation E = mc2 is one example of a beautiful equation. Another equation is F = G which is also simple and beautiful as it is applicable throughout the universe i.e. it is true for two small bodies and for planets and the value of G is same for. all cases.

Hence the equation in physics are more beautiful. F = G has been challenged at cosmic level on the basis of observations under a particular situation.

Question 15.
Though the statement quoted above be disputed, most physicists do have a feeling that the great laws of physics are at once simple and beautiful. Some of the notable physicists, besides Dirac, who have articulated this feeling are Einstein, Bohr, Heisenberg, Chandrasekhar and Feynman. You are urged to make special efforts to get access to the general books and writings by these and other great masters of physics (See the Bibliography at the end of this book). Their writings are truly inspiring.
Answer:
There is no doubt that great laws of physics are at once so simple and beautiful and are easy to grasp. For example, let us look at some of these:

1. E = mc2 is a famous Einstein’s mass energy equivalence relation which has a great impact not only on the various physical phenomena but also on the human lives.

2. Plank’s quantum condition i.e. E = hν is also a simple and beautiful equation and it is a great law of physics.

3. ∆x. ∆p ≥ $$\frac{1}{2}$$.$$\frac{h}{2π}$$ or ∆E.∆t ≥ $$\frac{1}{2}$$.$$\frac{h}{2π}$$ is Heisenberg’s
Uncertainity Principle which is also very simple, beautiful and interesting. It is a direct consequence of the dual nature of matter.

4. λ = $$\frac{h}{mv}$$ is also a famous equation in physics known as de-Broglie equation. It is again simple and beautiful.

Question 16.
Textbooks on science may give you a wrong impression that studying science is dry and all too serious and that scientists are absent minded introverts who never laugh or grin. This image of science and scientists is patently false. Scientists like any other group of humans have their share of humorists, and many have led their lives with a great sense of fun and adventure even as they seriously pursued their scientific work. Two great physicists of this genre are Gamow and Feynman. You will enjoy reading their books listed in the Bibliography?
Answer:
It is not an exercise as such but is a statement of fact. We can add the name of other scientist who were humorists along with being Physicists. They are C. V. Raman, Homi Jahangir Bhabha, Einstein and Bohr. India have several politicians like M.M. Joshi, V.P. Singh etc. who are Physicists. President A.P.J. Kalam is also a great nuclear scientist.