NCERT Solutions Class 11 Physics - Physical World

Albert Einstein

Ans:  Einstein's quote means that the world is very complex, with different sizes, spaces, and times. But even though it's so complicated, we can still understand it using a few simple rules or laws. That's why it's surprising (or "incomprehensible") that something so big and complicated can actually be understood.

Q.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.

At first, new ideas in science often seem strange or wrong, which is referred to as "heresy". But later, when people understand them better, these ideas are accepted as true, which is referred to as "dogma".

Ans:  For example, people used to think that light only travels in straight lines in a uniform media. When Huygens said light moves in waves, people thought he was wrong. Later, when things like interference and refraction were explained using waves, his idea was accepted.

Similarly, people believed light was just energy. But when the photoelectric effect was discovered, the idea that light might alsoconsist of particles was widely debated. Eventually, Einstein proved this with his quantum theory of light, and now it’s accepted as true.

Q.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.
Ans: In politics, leaders try to make things happen in any way possible to win people's support. In science, researchers observe things in the world and work to explain them with rules and laws. Many phenomena in the universe can be explained by established scientific laws, although some remain complex and not fully understood.

For example, the rule "F = mg" applies to both small objects and huge stars. This shows that science can solve or explain these phenomena, just like politics makes things possible. That’s why science is called "the art of the soluble," meaning it can find solutions to problems.

Q.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, which in your view have hindered the advancement of science in India.
Ans:  There are several reasons why science in India has not advanced as much as it could:

• There isn’t enough money or good infrastructure for high-quality research.
• Scientists are paid less than people in administrative positions, and they don’t have as many facilities.
• The focus of science education is inadequate. It doesn’t meet the needs of industries, which rely on new technology. Industrialists don’t trust Indian scientists much, and there’s very little collaboration between them.
• Science education in rural areas is almost absent, so most people don’t get the benefits of new technology and advancements in science.

Q.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?

Ans: Electrons cannot be observed directly with the naked eye, but their effects like electricity have been consistently observed and proven through experiments. On the other hand, for things like spirits and ghosts, even though people claim to see them, there is no scientific proof or successful tests. So, we cannot be 100% sure that they exist. Hence clearly, the comparison between these two cases lacks meaning.

Q.1.6. 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 inscrutable ways immortalized his face by imprinting it on the crab shells in that area.
(b) After the sea tragedy, fishermen in that area, in a gesture of honor 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.

 This interesting illustration taken from Carl Sagan’s ‘The Cosmos’ highlights the fact that often, strange and inexplicable phenomena that initially appear ‘supernatural’ may actually have simple scientific explanations. Try to think out other examples of this kind.

Ans: Explanation (b) is correct is a scientific explanation of the observed fact as it is backed by the scientific theory of 'evolution by artificial selection'.

Q.1.7. 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?

Ans: Here are the main scientific and technological breakthroughs that fueled the Industrial Revolution in England and Western Europe between 1750 and 1870:

• Steam Engine: Invented by British inventor James Watt in 1769, it utilized heat and thermodynamics. It allowed factories to be built away from rivers, as machines could now be powered by steam.
• Blast Furnace: Enabled the cheap conversion of low-grade iron into steel.
• Cotton Gin (Spinning Jenny): Greatly sped up the process of removing seeds from cotton, doing it 300 times faster than by hand.
• Electricity: The discovery of electricity led to the development of dynamos and electric motors.
• Explosives: These innovations not only aided the military but also advanced mineral exploration.
• Study of Motion: Research into gravitation contributed to the design of guns and cannons.
• Power Loom: This machine, powered by steam, revolutionized spinning and weaving in the textile industry.
• Safety Lamp: Allowed miners to work safely in mines.

Q.1.8. It is often said that the world is witnessing now a second industrial revolution, which will transform society as radically as did the first. List some key contemporary areas of science and technology, which are responsible for this revolution.

Ans: We are seeing a new industrial revolution, and it’s bringing big changes to society. Some of the important areas in science and technology leading this change are:

• Artificial intelligence
• Very fast computers
• Biotechnology (using biology to make new products)
• Creating materials that can conduct electricity at normal temperatures

Advances in:

• Electronics
• Information technology (like the internet)
• Nanotechnology (working with very tiny particles)
• Space science (exploring space and planets)

Q.1.9. Write in about 100 words a fiction piece based on your speculation on the science and technology of the twenty-second century.
Ans: Imagine a spaceship traveling toward a star 100 light years away. 

• It moves using electric current generated by electromagnetic induction as it crosses magnetic fields in space. The current powers an electric motor made of superconducting wires, so minimal energy is needed for the entire journey.
• However, in one area of space, the temperature rises so much that the superconducting wires lose their properties, causing the motor to stop working and creating panic on board because power is lost.
• In an instant, another spaceship arrives to help. It carries matter and antimatter stored in separate compartments, which are used to produce energy for the first ship. 
• This allows the first spaceship to continue its journey.

Q.1.10. Attempt to formulate your ‘moral’ views on the practice of science. Imagine yourself stumbling upon a discovery, which has great academic interest but is certain to have nothing but dangerous consequences for human society. How, if at all, will you resolve your dilemma?

Ans: A scientist's job is to discover the truth. Every discovery teaches us something about nature. So, whether a discovery is good or bad for people, it should be shared. However, we must consider the consequences before sharing it. If a discovery could harm people, it’s better to keep it limited to only the scientists working on it. This approach allows the discovery to be useful in the future while preventing current harm.

Q.1.11. 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:

(a) Mass vaccination against small pox to curb and finally eradicate this disease

from the population. (This has already been successfully done in India).

(b) Television for eradication of illiteracy and for mass communication of news and

ideas.

(c) Prenatal sex determination

(d) Computers for increase in work efficiency

(e) Putting artificial satellites into orbits around the Earth

(f ) Development of nuclear weapons

(g) Development of new and powerful techniques of chemical and biological warfare).

(h) Purification of water for drinking

(i) Plastic surgery

(j ) Cloning

Ans: 

(a) Good, Mass vaccination helped eradicate the dreaded diseases from the Earth.

(b) Good, Television helps in the literacy campaign and is an effective method of mass communication and entertainment.

(c) Bad, Prenatal sex determination is considered bad because it gives rise to the practice of abortion in the case of the female fetus.

(d)  Good, Computers increase work efficiency.

(e)  Good, Artificial satellites help in the worldwide communication process.

(f)  Bad, Nuclear weapons have the potential to cause mass destruction, posing a threat to humanity.

(g)  Bad, There is a risk that these techniques could be misused for destructive purposes.

(h) Good, Purified water improves the health of people.

(i)  Neither good nor bad. Plastic surgery is something that can’t be classified as either good or bad because it helps to remove a certain type of deformations in needy persons.

(j) Good, Cloning has the potential to ruin the normal family life of human society.

Q.1.12. 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 obscurantist 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?
Ans:  Poverty and illiteracy are the two major factors that make people superstitious in India. So to remove the superstitious and obscurantist attitude we have to first overcome these factors. Everybody should be educated so that one can have a scientific attitude. Knowledge of science can be put to use to prove people's superstitious wrong by showing them the scientific logic behind everything happening in our world.

Q.1.13. 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.
Ans: There is no real difference between men and women when it comes to work, intelligence, or decision-making. Nature doesn’t create major differences in the bodies or feelings of men and women. A balanced diet during pregnancy and after birth helps both men and women grow equally. If women get the same opportunities as men, they will be just as capable.

Many great women have excelled in various fields, such as:

• Madame Curie
• Indira Gandhi
• Florence Nightingale
• Margaret Thatcher
• Mother Teresa
• Sarojini Naidu
• Kalpana Chawla

These women, from different areas like science and sociology, have made a big impact on the world. Looking at the contributions women make in all aspects of life, it's clear that women are just as important to society as men.

Q.1.14. “It is more important to have beauty in the equations 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 that strike you as beautiful.
Ans. An equation that agrees with an experiment must also be simple and hence beautiful. We have some simple and beautiful equations in Physics such as:

• E = mc² (Energy equivalent of mass)
• E = hν (Energy of a photon)
• KE = 1/2 mv² (Kinetic energy of a moving particle)
• PE = mg (Potential energy of a body at rest)
• W = F.d (Work done)

All have the same dimensions. One experiment shows the dependency of energy on speed, while the other shows the dependency on frequency and displacement. This illustrates the beauty of physics equations that arise from various experiments.