# Class 11 Physics Chapter 1 Important Questions Physical World

Q.1. What is physics? Ans. Physics is the branch of science dealing with the nature and natural phenomena. Q.2. What is the basic difference between

It is important for the students that all the concepts should be very clear for better marks in future. Here, we are providing important conceptual questions and answers for class 11 physics chapter 1 physical world. In this lesson, students will learn about Physical World. This will not only help the students to know the important questions but will also help them during revision.

Q.1. What is physics?
Ans. Physics is the branch of science dealing with the nature and natural phenomena.

Q.2. What is the basic difference between science and technology?
Ans. Science is the study of laws of nature while technology is the application of these laws in practical situation.

Q.3. What is the scientific principle on which rocket propulsion is based?
Ans. Newton's second and third laws of motion.

Q.4. Name the principle on which a nuclear reactor works.
Ans. Nuclear fission.

Q.5. What is the scientific principle which forms the basis of heat engine and refrigerator?
Ans. Laws of thermodynamics.

Q.6. Who discovered the law of gravitation?
Ans. Sir Isaac Newton.

Ans. Becquerel, Pierre Curie and Marie Curie.

Q.8. Name a few Indian science physicists, who have made significant contributions in the field of physics.
Ans. C.V. Raman, S. Chandra Shekhar, S.N. Bose, Meghnad Saha and Homi J. Bhabha.

Q.9. What is gravitational force?
Ans. It is the force of attraction between two objects due to their masses.

Q.10. What is electromagnetic force?
Ans. It is the force of attraction or repulsion between two electric charges in motion.

Q.11. What is nuclear force?
Ans. The force between protons and neutrons inside the nucleus is called nuclear force.

Q.12. State law of conservation of linear momentum.
Ans. It states that if no external force acts on a system, the linear momentum of the system remains constant.

Q.13. State law of conservation of angular momentum.
Ans. It states that if no external torque acts on a system, then the total angular momentum of the system always remains constant.

Q.14. State law of conservation of energy.
Ans. It states that energy can neither be created nor destroyed, however, it may change from one form to another.

Q.15. Why do we call physics an exact science?
Ans. In physics, much importance is given to measurement and for this reason, it is sometimes called as an exact science or the science of measurement.

Q.16. Discuss relation of physics to chemistry.
Ans. The study of structure of atom, radioactivity, xray diffraction etc. has brought about a revolution in the present century chemistry. These studies have led to the rearrangement of elements in the periodic table, to detect even traces of substances in a sample, to know the nature of valency and chemical bonding and to understand the complex chemical structure.

Q.17. Explain in brief the relation of physics to biological sciences.
Ans. The life sciences have also been benefited by the advancements in physics. Optical microscope is found to be of immense used in the study of biology. The electron microscope has made it possible to see even the structure of a cell. The X-ray and the neutron diffraction have helped in understanding the structure of nucleic acids, which have helped to control the vital processes on the life activity.

Q.18. Name two advancements made in technology on the basis of physics.
Ans.

• (a) The discovery of nuclear fission has proved to be a tremendous source of energy. In nuclear power stations and nuclear bombs, large amount of energy becomes available due to the conversion of mass into energy.
• (b) The earth satellites are being successfully used to forecast the weather very accurately.

Q.19. List some key contemporary areas of science and technology, which are responsible for the present industrial revolution.
Ans.

• (a) The study of liver systems has helped to design a large number of very useful machines.
• (b) The phenomenon of electromagnetic induction has led to the development of electric motors and generators.
• (c) Thermodynamics has led us to design heat engines and refrigerators.
• (d) The discovery of nucleus fission has proved to be a tremendous source of energy in nuclear power stations a large amount of energy becomes available due to conversion of mass into energy.

Q.20. What is mechanics?
Ans. Mechanics is the theory of motion of material objects at low speeds.

Q.21. What is thermodynamics?
Ans. Thermodynamics is the theory of heat, temperature and the behaviour of a system of a large number of particles.

Q.22. What is electromagnetism?
Ans. Electromagnetism is the theory of electricity magnetism and electromagnetic radiation.

Q.23. What is relativity?
Ans. Relativity is the theory of invariance in nature and the theory covering the motion of high speed moving particles.

Q.24. what is quantum mechanics?
Ans. Quantum mechanics is the theory of mechanical behaviour of sub-microscopic particles.

Q.25. Who discovered X-rays?
Ans. Roentgen.

Q.26. Who discovered the law of photoelectricity?
Ans. Albert Einstein.

Q.27. Name the principle on which optical fibres work?
Ans. Total internal reflection of light.

Q.28. Name the scientist who discovered electromagnetic waves.
Ans. Hertz.

Q.29. Name the scientific principle on which electric generator works.
Ans. Electromagnetic induction.

Q.30. Name the scientist who discovered the structure and evolution of stars.
Ans. S. Chandrasekhar.

Q.31. Which force is the strongest force operating in nature?
Ans. The nuclear force is the strongest force operating in nature.

Q.32. Which force is the weakest force operating in nature?
Ans. The gravitational force is the weakest force operating in nature.

Q.33. What is the field particle of gravitational force?
Ans. The graviton is the field particle of gravitational force.

Q.34. What is the field particle of electromagnetic force?
Ans. The photon is the field particle of electromagnetic force.

Q.35. How much stronger is the electromagnetic force then the gravitational force?
Ans. The electromagnetic force is about 1036 times stronger than the gravitational force.

Q.36. How much stronger is nuclear force than the gravitational force?
Ans. The nuclear force is about 1038 times stronger than the gravitational force.

Q.37. Who discovered quantum mechanics?
Ans. Heisenberg

Q.38. Name the principle on which radio and television works.
Ans. Propagation of electromagnetic waves.

Q.39. What is the scientific principle on which Sonar works?
Ans. Reflection of ultrasonic waves.

Q.40. Does imagination play any role in physics?
Ans. The imagination plays a pivotal role in physics. A large number of discoveries made in the field of physics are the results of their imagination of their discoveries. Following are a few examples :-

• (a) The imagination of flying like a bird in the open sky led to the development of aircrafts.
• (b) The imagination that there may be life on the other planets led to the beginning of space flights.
• (c) The imagination that one may communicate with people at far off places led to the discovery of telephone and radio-communication