NCERT Solutions Class 11 Physics Chapter 1 - Physical World

NCERT Solutions for Class 11 Physics Chapter 1 - Physical World

EXERCISES

1.1 Some of the most meaningful advances in physics have come from discoveries of unexpected phenomena during experiments. What does this suggest about the nature of the physical world?

Solution: The nature of physical world reveals that it has amazing regularity and beautiful simplicity. Many physical phenomena are so complex that their exact prediction is not easy. However, some times the most meaningful discoveries in physics have come when experiments revealed unexpected phenomena that gave new insights into the nature of the physical world. For example:

• Discovery of radioactivity by Henri Becquerel
• Discovery of electromagnetic waves by Hertz
• Discovery of X-rays by Roentgen This suggests that physical world has underlying unity and systematic relationships.

1.2 Why do we study physics?

Solution: We study physics because:

1. Physics provides basic understanding of natural phenomena
2. It develops scientific thinking and rational approach
3. Physics has led to technological developments that benefit humanity
4. It satisfies human curiosity about nature
5. Physics theories have aesthetic appeal and mathematical beauty
6. It forms the foundation for other sciences like chemistry and biology

1.3 The Nobel Prize in Physics in 2020 was awarded to Roger Penrose, Reinhard Genzel, and Andrea Ghez for their discoveries about black holes. This shows that fundamental physics is still an active field. Give examples of some fundamental physics problems that are currently being investigated.

Solution: Current fundamental physics problems being investigated:

1. Dark matter and dark energy - about 95% of universe composition is unknown
2. Quantum gravity - unification of quantum mechanics and general relativity
3. Origin of mass - understanding Higgs mechanism completely
4. Unification of fundamental forces
5. Nature of time and causality
6. Quantum foundations and measurement problem
7. Extra dimensions and string theory
8. Cosmic inflation and multiverse

1.4 What are the two main thrusts for physics research today?

Solution: The two main thrusts for physics research today are:

1. Unification: Attempting to unify the fundamental forces of nature under single theoretical framework
2. Reductionism: Explaining complex phenomena in terms of elementary constituents and interactions

Additional Exercises:

1.5 What is the difference between macroscopic and microscopic domains of physics?

Solution: Macroscopic domain:

• Deals with large-scale phenomena
• Objects visible to naked eye
• Classical physics applies
• Examples: planetary motion, heat engines, electromagnetic devices

Microscopic domain:

• Deals with atomic and subatomic particles
• Objects not visible to naked eye
• Quantum physics applies
• Examples: atomic structure, nuclear physics, particle physics

1.6 How has physics influenced technology? Give examples.

Solution: Physics has greatly influenced technology:

1. Electricity and magnetism → Electrical devices, motors, generators
2. Quantum mechanics → Computers, lasers, MRI machines
3. Nuclear physics → Nuclear power, radiotherapy
4. Optics → Cameras, telescopes, fiber optic communication
5. Thermodynamics → Heat engines, refrigeration
6. Mechanics → Transportation systems