Physical World — Class 11 MCQs with Answers

Physical World — important questions & MCQs with answers (Class 11 Physics)

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   Physics is the study of:

   ALiving organisms onlyBLanguagesCNumbers onlyDMatter, energy and their interactions
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   Answer: Matter, energy and their interactions

   Explanation: Physics is the science of matter, energy and their interactions, from atoms to galaxies. 'Numbers only' is mathematics, and 'living organisms only' is biology, not physics.

2. Q2 of 6Easy

   Number of fundamental forces in nature:

   A2B3C4D5
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   Answer: 4

   Explanation: Physics counts four fundamental forces: gravity, electromagnetic, weak nuclear and strong nuclear. Forgetting the weak force and stopping at 3 is the usual undercount.

3. Q3 of 6Medium

   Ratio of electrostatic to gravitational force between electron and proton is approximately:

   A10⁻³⁹B10¹C1D10³⁹ (electrostatic vastly stronger)
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   Answer: 10³⁹ (electrostatic vastly stronger)

   Explanation: For an electron-proton pair, the Coulomb force e²/(4πε₀r²) exceeds the gravitational force Gm_em_p/r² by a factor of about 10³⁹, since gravity is by far the weakest fundamental force.

4. Q4 of 6Medium

   Nobel Prize-winning Indian scientist for Raman scattering:

   AC. V. Raman (1930)BBoseCChandrasekharDSaha
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   Answer: C. V. Raman (1930)

   Explanation: C. V. Raman won the 1930 Nobel Prize in Physics for the Raman effect — light changing wavelength when it inelastically scatters off molecules — the first Indian Nobel laureate in science.

5. Q5 of 6Hard

   Maxwell unified:

   ASound and lightBGravity and heatCElectricity, magnetism and opticsDNone
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   Answer: Electricity, magnetism and optics

   Explanation: Maxwell's equations showed electricity, magnetism and optics are one phenomenon — light itself is an oscillating EM wave. That differs from Newton's unifying gravity across Earth and the planets.

6. Q6 of 6Hard

   Weak nuclear force is responsible for:

   AMagnetismBBeta decayCFrictionDSurface tension
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   Answer: Beta decay

   Explanation: Beta decay, where a neutron converts to a proton emitting an electron and antineutrino, is driven by the weak nuclear force — not the strong force, which instead holds the nucleus together.

Physical World notes: key concepts (Class 11 Physics)

Physical World is a qualitative orientation to physics itself: the enormous range of scales it studies, its two great strategies of unification and reduction, the four fundamental forces that underlie every interaction in nature, and the conservation laws and symmetries that any acceptable physical theory must respect.

Scope of physics

Physics studies matter, energy and their interactions across an enormous span — from nuclei at about 10⁻¹⁴ m to the observable universe at about 10²⁶ m — the widest reach of any science.

Macroscopic domain

Classical physics — mechanics, thermodynamics and electromagnetism — describes laboratory, terrestrial and astronomical phenomena where quantum effects are negligible.

Microscopic domain

Quantum theory governs atomic, molecular and nuclear phenomena, where energy and other quantities come in discrete packets rather than continuous amounts.

Unification

A principal thrust of physics: explaining diverse phenomena with a few universal laws, as when electricity, magnetism and optics were merged into electromagnetism.

Reduction

The complementary strategy of understanding a complex system through its constituent parts and their interactions — for instance, deriving thermodynamics from molecular motion.

Gravitational force

The weakest fundamental force (relative strength ~10⁻³⁹) but infinite in range and always attractive; it dominates at astronomical scales because bulk matter is electrically neutral.

Electromagnetic force

Acts between charges, about 10³⁶ times stronger than gravity, infinite in range and both attractive and repulsive; it binds electrons to nuclei and holds all bulk matter together.

Strong nuclear force

The strongest force (taken as relative strength 1) and charge-independent, but extremely short-ranged (~10⁻¹⁵ m); it binds protons and neutrons inside the nucleus.

Weak nuclear force

A very short-ranged force (~10⁻¹⁶ m, relative strength ~10⁻¹³) that governs beta decay and inter-conversion of neutrons and protons; weaker than electromagnetism but stronger than gravity.

Conservation laws

Energy, linear momentum, angular momentum and electric charge stay constant in an isolated system, and these laws hold across both classical and quantum physics.

Symmetry and conservation

Each conservation law reflects a symmetry of nature — energy conservation follows from invariance under time translation, momentum from homogeneity of space (Noether's insight).

Nature of physical laws

Physical laws are universal, expressed mathematically and validated by reproducible experiment; a single reliable contrary observation is enough to overturn a proposed law.