CLASS 11 PHYSICS • REVISION AND PYQS

Physical World Formulas and PYQs

Complete revision of Physical World with definitions, scientific method, fundamental forces, NCERT questions, NEET-style questions, CBSE school questions, assertion-reason and case studies.

CBSENEETJEE MainJEE AdvancedIBIGCSEA-Level

Need help in Class 11 Physics, CBSE, NEET, JEE, IB or IGCSE?

Contact Kumar Sir for one-to-one online Physics classes.

Phone: +91-9958461445Email: kumarsirphysics@gmail.com Website: https://kumarphysicsclasses.com WhatsApp to Kumar Sir

1. Complete Chapter Summary

Physics and Scope

Physics studies matter, energy, motion, space, time and natural laws. Its scope extends from subatomic particles to the universe.

Scientific Method

Observation, question, hypothesis, experiment, data collection, analysis and theory or law form the scientific method.

Forces and Society

Fundamental forces explain interactions; Physics supports technology, healthcare, communication, energy and sustainable development.

Models

Models simplify reality. They are useful for prediction but have limited validity.

Measurement

Accuracy, precision, significant figures and errors decide the quality of data.

Exam Core

Most questions test examples, definitions, theory vs law, model limitations and force comparisons.

2. Important Definitions

Physics

Study of matter, energy, motion, space, time and laws of nature.

Natural Science

Science that studies natural phenomena through observation and experiment.

Observation

Careful and objective noting of a phenomenon.

Experiment

Controlled test of a hypothesis.

Hypothesis

Testable prediction or tentative explanation.

Scientific Theory

Well-tested explanation of observations.

Scientific Law

Verified relation or pattern in nature.

Model

Simplified representation of a real system.

Fundamental Force

Basic interaction of nature.

Gravitational Force

Attractive force between masses.

Electromagnetic Force

Force between charges.

Strong Nuclear Force

Force binding nucleons inside nucleus.

Weak Nuclear Force

Force responsible for beta decay.

Accuracy

Closeness to true value.

Precision

Closeness of repeated readings.

Significant Figures

Meaningful digits in a measured value.

Measurement Error

Difference or uncertainty in measured value.

Technology

Application of science to practical devices.

Scientific Method

Systematic process for building scientific knowledge.

3. Force Comparison Table

Force	Relative Strength	Range	Nature	Acts On	Example
Strong Nuclear Force	1	~10^-15 m	Attractive at nuclear range	Nucleons	Nuclear binding
Electromagnetic Force	10^-2	Infinite	Attractive or repulsive	Charges	Atoms, light, chemical bonding
Weak Nuclear Force	10^-13	~10^-18 m	Particle transformation	Quarks and leptons	Beta decay
Gravitational Force	10^-38	Infinite	Always attractive	Masses	Planets, galaxies

4. Scientific Method Summary

Scientific method turns observations into reliable knowledge using testable hypotheses and experiments.

Simple Pendulum

Tests relation between length and time period.

Ohm's Law

Tests relation between V and I.

Free Fall

Studies acceleration due to gravity.

Refraction

Studies bending of light at interface.

5. NCERT Questions

NCERT-style Q1

Question: What is Physics?

Answer: Physics is the study of nature and natural laws.

Explanation: It explains matter, energy, motion and interactions.

Exam Tip: Use broad definition.

NCERT-style Q2

Question: Why is scientific method important?

Answer: It makes knowledge testable and reliable.

Explanation: It avoids guesswork by using experiment and evidence.

Exam Tip: Write steps in order.

NCERT-style Q3

Question: Differentiate theory and law.

Answer: Theory explains; law describes.

Explanation: A theory gives mechanism, a law gives relation.

Exam Tip: This is a common exam question.

NCERT-style Q4

Question: Why are models used?

Answer: Models simplify complex systems.

Explanation: They help prediction but have limitations.

Exam Tip: Mention limitations.

NCERT-style Q5

Question: Why does gravity dominate astronomy?

Answer: It has infinite range and is always attractive.

Explanation: Large masses make gravity important despite weakness.

Exam Tip: Do not write gravity is strongest.

6. CBSE School Level Questions

1-mark

Question: Define observation.

Answer: Careful noticing of a phenomenon.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

1-mark

Question: Name the strongest fundamental force.

Answer: Strong nuclear force.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

2-mark

Question: Write two uses of Physics in society.

Answer: Healthcare and communication technologies use Physics.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

2-mark

Question: State two limitations of models.

Answer: Models are simplified and valid only under certain conditions.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

3-mark

Question: Explain scientific method.

Answer: Observation leads to question, hypothesis, experiment, result and theory or law.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

3-mark

Question: Compare accuracy and precision.

Answer: Accuracy is closeness to true value; precision is closeness among repeated readings.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

5-mark

Question: Explain scope of Physics.

Answer: Physics covers particles, atoms, matter, motion, heat, light, electricity, nuclei, stars and universe.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

5-mark

Question: Explain Physics and technology.

Answer: Physics enables mobile phones, MRI, lasers, satellites, solar panels, computers and nuclear energy.

Explanation: A school answer should define and give examples.

Exam Tip: Keep answers point-wise.

7. NEET-Style 60 MCQs

Concept check 1

Question: Physics is best described as the study of

(a) matter, energy and natural laws(b) Only living organisms(c) Only chemical reactions(d) Only planets

Correct Answer: matter, energy and natural laws

Explanation: Physics studies matter, energy, motion, space, time and laws of nature.

Exam Tip: Remember the broad definition.

Revision MCQ 2

Question: A testable prediction is called a

(a) hypothesis(b) law(c) unit(d) dimension

Correct Answer: hypothesis

Explanation: A hypothesis must be testable by experiment.

Exam Tip: Testable is the keyword.

Exam focus 3

Question: The force with relative strength 10^-38 is

(a) gravitational(b) electromagnetic(c) weak nuclear(d) strong nuclear

Correct Answer: gravitational

Explanation: Gravity is weakest in relative strength comparison.

Exam Tip: Weakest force is gravity.

Concept check 4

Question: The strongest fundamental force is

(a) strong nuclear(b) weak nuclear(c) gravitational(d) frictional

Correct Answer: strong nuclear

Explanation: Strong force binds nucleons in the nucleus.

Exam Tip: Strong means nuclear binding.

Revision MCQ 5

Question: Electromagnetic force acts on

(a) charges(b) only masses(c) only neutrons(d) only photons

Correct Answer: charges

Explanation: It acts between charged particles.

Exam Tip: Charge means EM force.

Exam focus 6

Question: Weak nuclear force is responsible for

(a) beta decay(b) chemical bonding(c) tides(d) normal reaction

Correct Answer: beta decay

Explanation: Weak interaction causes beta decay.

Exam Tip: Beta decay identifies weak force.

Concept check 7

Question: Accuracy means closeness to

(a) true value(b) other readings(c) zero(d) least count

Correct Answer: true value

Explanation: Accuracy compares measurement with true value.

Exam Tip: Accuracy = true value closeness.

Revision MCQ 8

Question: Precision means closeness of

(a) repeated readings(b) reading to true value(c) error to zero(d) force to mass

Correct Answer: repeated readings

Explanation: Precision is repeatability.

Exam Tip: Precision = repeatability.

Exam focus 9

Question: Zeros before non-zero digits in 0.00340 are

(a) not significant(b) always significant(c) negative(d) units

Correct Answer: not significant

Explanation: Leading zeros only locate decimal point.

Exam Tip: Leading zeros do not count.

Concept check 10

Question: The model that treats gas molecules as point particles is

(a) ideal gas model(b) ray model(c) Bohr model(d) solar model

Correct Answer: ideal gas model

Explanation: Ideal gas model simplifies real gases.

Exam Tip: Models have assumptions.

Revision MCQ 11

Question: Scientific law mainly

(a) describes a relation(b) is a blind guess(c) cannot be tested(d) is always false

Correct Answer: describes a relation

Explanation: Laws describe patterns or mathematical relations.

Exam Tip: Theory explains; law describes.

Exam focus 12

Question: Scientific theory mainly

(a) explains observations(b) is less tested than hypothesis(c) is not scientific(d) means opinion

Correct Answer: explains observations

Explanation: A theory is a well-tested explanation.

Exam Tip: Theory is not casual opinion.

Concept check 13

Question: Which has infinite range?

(a) gravitational force(b) strong nuclear force(c) weak nuclear force(d) contact friction only

Correct Answer: gravitational force

Explanation: Gravity and EM have infinite range.

Exam Tip: Nuclear forces are short range.

Revision MCQ 14

Question: Which force can be attractive or repulsive?

(a) electromagnetic(b) gravitational(c) strong only(d) weak only

Correct Answer: electromagnetic

Explanation: Like charges repel and unlike charges attract.

Exam Tip: Gravity is only attractive.

Exam focus 15

Question: A model is used because reality is often

(a) complex(b) always wrong(c) unmeasurable only(d) not natural

Correct Answer: complex

Explanation: Models simplify complex systems.

Exam Tip: Model = simplified representation.

Concept check 16

Question: Ohm’s law is an example of a

(a) scientific law(b) hypothesis only(c) biological theory(d) random error

Correct Answer: scientific law

Explanation: It describes relation between V and I under fixed conditions.

Exam Tip: Law describes relation.

Revision MCQ 17

Question: Kinetic theory of gases is a

(a) scientific theory(b) unit(c) least count(d) fundamental force

Correct Answer: scientific theory

Explanation: It explains pressure and temperature using molecular motion.

Exam Tip: Theory explains.

Exam focus 18

Question: The range of strong nuclear force is about

(a) 10^-15 m(b) 10^-38 m(c) infinite(d) 1 m

Correct Answer: 10^-15 m

Explanation: Strong force acts inside nucleus.

Exam Tip: Strong range: nuclear size.

Concept check 19

Question: The range of weak nuclear force is about

(a) 10^-18 m(b) 10^-2 m(c) infinite(d) 10⁸ m

Correct Answer: 10^-18 m

Explanation: Weak force acts at sub-nuclear scale.

Exam Tip: Weak range is shortest.

Revision MCQ 20

Question: A systematic error usually affects readings

(a) in one direction(b) randomly only(c) never(d) only after averaging

Correct Answer: in one direction

Explanation: Calibration or zero error shifts readings consistently.

Exam Tip: Systematic = biased.

Exam focus 21

Question: Physics is best described as the study of

(a) matter, energy and natural laws(b) Only living organisms(c) Only chemical reactions(d) Only planets

Correct Answer: matter, energy and natural laws

Explanation: Physics studies matter, energy, motion, space, time and laws of nature.

Exam Tip: Remember the broad definition.

Concept check 22

Question: A testable prediction is called a

(a) hypothesis(b) law(c) unit(d) dimension

Correct Answer: hypothesis

Explanation: A hypothesis must be testable by experiment.

Exam Tip: Testable is the keyword.

Revision MCQ 23

Question: The force with relative strength 10^-38 is

(a) gravitational(b) electromagnetic(c) weak nuclear(d) strong nuclear

Correct Answer: gravitational

Explanation: Gravity is weakest in relative strength comparison.

Exam Tip: Weakest force is gravity.

Exam focus 24

Question: The strongest fundamental force is

(a) strong nuclear(b) weak nuclear(c) gravitational(d) frictional

Correct Answer: strong nuclear

Explanation: Strong force binds nucleons in the nucleus.

Exam Tip: Strong means nuclear binding.

Concept check 25

Question: Electromagnetic force acts on

(a) charges(b) only masses(c) only neutrons(d) only photons

Correct Answer: charges

Explanation: It acts between charged particles.

Exam Tip: Charge means EM force.

Revision MCQ 26

Question: Weak nuclear force is responsible for

(a) beta decay(b) chemical bonding(c) tides(d) normal reaction

Correct Answer: beta decay

Explanation: Weak interaction causes beta decay.

Exam Tip: Beta decay identifies weak force.

Exam focus 27

Question: Accuracy means closeness to

(a) true value(b) other readings(c) zero(d) least count

Correct Answer: true value

Explanation: Accuracy compares measurement with true value.

Exam Tip: Accuracy = true value closeness.

Concept check 28

Question: Precision means closeness of

(a) repeated readings(b) reading to true value(c) error to zero(d) force to mass

Correct Answer: repeated readings

Explanation: Precision is repeatability.

Exam Tip: Precision = repeatability.

Revision MCQ 29

Question: Zeros before non-zero digits in 0.00340 are

(a) not significant(b) always significant(c) negative(d) units

Correct Answer: not significant

Explanation: Leading zeros only locate decimal point.

Exam Tip: Leading zeros do not count.

Exam focus 30

Question: The model that treats gas molecules as point particles is

(a) ideal gas model(b) ray model(c) Bohr model(d) solar model

Correct Answer: ideal gas model

Explanation: Ideal gas model simplifies real gases.

Exam Tip: Models have assumptions.

Concept check 31

Question: Scientific law mainly

(a) describes a relation(b) is a blind guess(c) cannot be tested(d) is always false

Correct Answer: describes a relation

Explanation: Laws describe patterns or mathematical relations.

Exam Tip: Theory explains; law describes.

Revision MCQ 32

Question: Scientific theory mainly

(a) explains observations(b) is less tested than hypothesis(c) is not scientific(d) means opinion

Correct Answer: explains observations

Explanation: A theory is a well-tested explanation.

Exam Tip: Theory is not casual opinion.

Exam focus 33

Question: Which has infinite range?

(a) gravitational force(b) strong nuclear force(c) weak nuclear force(d) contact friction only

Correct Answer: gravitational force

Explanation: Gravity and EM have infinite range.

Exam Tip: Nuclear forces are short range.

Concept check 34

Question: Which force can be attractive or repulsive?

(a) electromagnetic(b) gravitational(c) strong only(d) weak only

Correct Answer: electromagnetic

Explanation: Like charges repel and unlike charges attract.

Exam Tip: Gravity is only attractive.

Revision MCQ 35

Question: A model is used because reality is often

(a) complex(b) always wrong(c) unmeasurable only(d) not natural

Correct Answer: complex

Explanation: Models simplify complex systems.

Exam Tip: Model = simplified representation.

Exam focus 36

Question: Ohm’s law is an example of a

(a) scientific law(b) hypothesis only(c) biological theory(d) random error

Correct Answer: scientific law

Explanation: It describes relation between V and I under fixed conditions.

Exam Tip: Law describes relation.

Concept check 37

Question: Kinetic theory of gases is a

(a) scientific theory(b) unit(c) least count(d) fundamental force

Correct Answer: scientific theory

Explanation: It explains pressure and temperature using molecular motion.

Exam Tip: Theory explains.

Revision MCQ 38

Question: The range of strong nuclear force is about

(a) 10^-15 m(b) 10^-38 m(c) infinite(d) 1 m

Correct Answer: 10^-15 m

Explanation: Strong force acts inside nucleus.

Exam Tip: Strong range: nuclear size.

Exam focus 39

Question: The range of weak nuclear force is about

(a) 10^-18 m(b) 10^-2 m(c) infinite(d) 10⁸ m

Correct Answer: 10^-18 m

Explanation: Weak force acts at sub-nuclear scale.

Exam Tip: Weak range is shortest.

Concept check 40

Question: A systematic error usually affects readings

(a) in one direction(b) randomly only(c) never(d) only after averaging

Correct Answer: in one direction

Explanation: Calibration or zero error shifts readings consistently.

Exam Tip: Systematic = biased.

Revision MCQ 41

Question: Physics is best described as the study of

(a) matter, energy and natural laws(b) Only living organisms(c) Only chemical reactions(d) Only planets

Correct Answer: matter, energy and natural laws

Explanation: Physics studies matter, energy, motion, space, time and laws of nature.

Exam Tip: Remember the broad definition.

Exam focus 42

Question: A testable prediction is called a

(a) hypothesis(b) law(c) unit(d) dimension

Correct Answer: hypothesis

Explanation: A hypothesis must be testable by experiment.

Exam Tip: Testable is the keyword.

Concept check 43

Question: The force with relative strength 10^-38 is

(a) gravitational(b) electromagnetic(c) weak nuclear(d) strong nuclear

Correct Answer: gravitational

Explanation: Gravity is weakest in relative strength comparison.

Exam Tip: Weakest force is gravity.

Revision MCQ 44

Question: The strongest fundamental force is

(a) strong nuclear(b) weak nuclear(c) gravitational(d) frictional

Correct Answer: strong nuclear

Explanation: Strong force binds nucleons in the nucleus.

Exam Tip: Strong means nuclear binding.

Exam focus 45

Question: Electromagnetic force acts on

(a) charges(b) only masses(c) only neutrons(d) only photons

Correct Answer: charges

Explanation: It acts between charged particles.

Exam Tip: Charge means EM force.

Concept check 46

Question: Weak nuclear force is responsible for

(a) beta decay(b) chemical bonding(c) tides(d) normal reaction

Correct Answer: beta decay

Explanation: Weak interaction causes beta decay.

Exam Tip: Beta decay identifies weak force.

Revision MCQ 47

Question: Accuracy means closeness to

(a) true value(b) other readings(c) zero(d) least count

Correct Answer: true value

Explanation: Accuracy compares measurement with true value.

Exam Tip: Accuracy = true value closeness.

Exam focus 48

Question: Precision means closeness of

(a) repeated readings(b) reading to true value(c) error to zero(d) force to mass

Correct Answer: repeated readings

Explanation: Precision is repeatability.

Exam Tip: Precision = repeatability.

Concept check 49

Question: Zeros before non-zero digits in 0.00340 are

(a) not significant(b) always significant(c) negative(d) units

Correct Answer: not significant

Explanation: Leading zeros only locate decimal point.

Exam Tip: Leading zeros do not count.

Revision MCQ 50

Question: The model that treats gas molecules as point particles is

(a) ideal gas model(b) ray model(c) Bohr model(d) solar model

Correct Answer: ideal gas model

Explanation: Ideal gas model simplifies real gases.

Exam Tip: Models have assumptions.

Exam focus 51

Question: Scientific law mainly

(a) describes a relation(b) is a blind guess(c) cannot be tested(d) is always false

Correct Answer: describes a relation

Explanation: Laws describe patterns or mathematical relations.

Exam Tip: Theory explains; law describes.

Concept check 52

Question: Scientific theory mainly

(a) explains observations(b) is less tested than hypothesis(c) is not scientific(d) means opinion

Correct Answer: explains observations

Explanation: A theory is a well-tested explanation.

Exam Tip: Theory is not casual opinion.

Revision MCQ 53

Question: Which has infinite range?

(a) gravitational force(b) strong nuclear force(c) weak nuclear force(d) contact friction only

Correct Answer: gravitational force

Explanation: Gravity and EM have infinite range.

Exam Tip: Nuclear forces are short range.

Exam focus 54

Question: Which force can be attractive or repulsive?

(a) electromagnetic(b) gravitational(c) strong only(d) weak only

Correct Answer: electromagnetic

Explanation: Like charges repel and unlike charges attract.

Exam Tip: Gravity is only attractive.

Concept check 55

Question: A model is used because reality is often

(a) complex(b) always wrong(c) unmeasurable only(d) not natural

Correct Answer: complex

Explanation: Models simplify complex systems.

Exam Tip: Model = simplified representation.

Revision MCQ 56

Question: Ohm’s law is an example of a

(a) scientific law(b) hypothesis only(c) biological theory(d) random error

Correct Answer: scientific law

Explanation: It describes relation between V and I under fixed conditions.

Exam Tip: Law describes relation.

Exam focus 57

Question: Kinetic theory of gases is a

(a) scientific theory(b) unit(c) least count(d) fundamental force

Correct Answer: scientific theory

Explanation: It explains pressure and temperature using molecular motion.

Exam Tip: Theory explains.

Concept check 58

Question: The range of strong nuclear force is about

(a) 10^-15 m(b) 10^-38 m(c) infinite(d) 1 m

Correct Answer: 10^-15 m

Explanation: Strong force acts inside nucleus.

Exam Tip: Strong range: nuclear size.

Revision MCQ 59

Question: The range of weak nuclear force is about

(a) 10^-18 m(b) 10^-2 m(c) infinite(d) 10⁸ m

Correct Answer: 10^-18 m

Explanation: Weak force acts at sub-nuclear scale.

Exam Tip: Weak range is shortest.

Exam focus 60

Question: A systematic error usually affects readings

(a) in one direction(b) randomly only(c) never(d) only after averaging

Correct Answer: in one direction

Explanation: Calibration or zero error shifts readings consistently.

Exam Tip: Systematic = biased.

8. JEE Main PYQ-Style Questions

JEE Main Exam-style Question

Question: A model gives correct predictions only for small speeds. What does it show?

Answer: The model has a limited range of validity.

Explanation: Newtonian mechanics works well at ordinary speeds but fails near speed of light.

Exam Tip: Always mention valid conditions.

JEE Main Exam-style Question

Question: Match: gravity, EM, strong, weak with astronomy, atoms, nuclear binding, beta decay.

Answer: Gravity-astronomy, EM-atoms, strong-binding, weak-beta decay.

Explanation: Each force has a characteristic domain.

Exam Tip: Make association tables.

JEE Main Exam-style Question

Question: A reading is repeated with small scatter but large constant offset. Identify error.

Answer: Systematic error with high precision but poor accuracy.

Explanation: Small scatter means precision; offset means poor accuracy.

Exam Tip: Separate accuracy from precision.

JEE Main Exam-style Question

Question: If a law is verified by many experiments, can it still have limits?

Answer: Yes. Laws may be valid under specified conditions.

Explanation: Physical laws are tested in domains and may need deeper theory.

Exam Tip: Write domain of validity.

9. JEE Advanced Conceptual Questions

Advanced Concept 1

Question: Why can a simple model be scientifically valuable even if not completely true?

Answer: Because it can make accurate predictions within a limited domain.

Explanation: Models are judged by usefulness and validity range.

Exam Tip: Use phrase “domain of validity”.

Advanced Concept 2

Question: Explain why force strength and range are different ideas.

Answer: Strength measures relative magnitude, range measures distance of significant action.

Explanation: Strong force is strongest but short-range; gravity is weakest but infinite-range.

Exam Tip: Use strong vs gravity example.

Advanced Concept 3

Question: Why is Newtonian mechanics not discarded even after relativity?

Answer: It remains an excellent approximation at low speeds.

Explanation: Old theories may survive as limiting cases.

Exam Tip: Write “limiting case”.

Advanced Concept 4

Question: Why is dimensional thinking useful in Physical World?

Answer: It checks consistency of equations and identifies possible relations.

Explanation: Dimensions do not prove a formula but can reject wrong ones.

Exam Tip: Mention limitation too.

10. IB Physics Questions

IB Question 1

Question: Explain the role of uncertainty in scientific measurement.

Answer: Uncertainty shows the range within which the true value may lie.

Explanation: IB answers should mention reliability and limitations of instruments.

Exam Tip: Use language of uncertainty.

IB Question 2

Question: Why is model building important in science?

Answer: Models allow explanation and prediction while simplifying complex systems.

Explanation: IB emphasizes nature of science and limitations.

Exam Tip: Mention assumptions.

IB Question 3

Question: How can repeated trials improve reliability?

Answer: They reduce the effect of random errors and allow averaging.

Explanation: Repeated data helps identify scatter.

Exam Tip: Use “random error”.

IB Question 4

Question: What makes a theory scientific?

Answer: It must be evidence-based, testable and predictive.

Explanation: Scientific theories are not opinions.

Exam Tip: Use testable and falsifiable.

11. IGCSE Questions

IGCSE Question 1

Question: Identify independent variable in an experiment where length of pendulum is changed.

Answer: Length of pendulum.

Explanation: It is deliberately changed.

Exam Tip: Independent means changed by student.

IGCSE Question 2

Question: Why repeat measurements?

Answer: To reduce random error and calculate a reliable average.

Explanation: Repeats make results more dependable.

Exam Tip: Write average.

IGCSE Question 3

Question: What is precision?

Answer: Closeness of repeated readings.

Explanation: Precision is about repeatability.

Exam Tip: Do not confuse with accuracy.

IGCSE Question 4

Question: Give one example of a simple model.

Answer: Ray model of light.

Explanation: It simplifies light propagation as straight rays.

Exam Tip: Model examples score marks.

12. A-Level Questions

A-Level Question 1

Question: Explain validity of assumptions in a physical model.

Answer: Assumptions define when a model can be applied.

Explanation: If assumptions fail, predictions become unreliable.

Exam Tip: State assumptions clearly.

A-Level Question 2

Question: How many significant figures are in 3.00 × 10⁸?

Answer: Three significant figures.

Explanation: All digits in coefficient 3.00 are significant.

Exam Tip: Scientific notation clarifies precision.

A-Level Question 3

Question: Percentage error formula?

Answer: Percentage error = (absolute error / measured value) × 100.

Explanation: Use same units in numerator and denominator.

Exam Tip: Formula is Elementor-safe.

A-Level Question 4

Question: Why are fundamental interactions important?

Answer: They explain all known physical changes and structures.

Explanation: Forces underlie motion, binding and decay.

Exam Tip: Connect micro and macro scales.

13. Assertion Reason: 30 Questions

Assertion Reason 1

Assertion: Doping changes conductivity of a semiconductor.

Reason: Doping changes number of charge carriers.

Options: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true.

Answer: (a)

Explanation: Both are true and reason explains assertion.

Assertion Reason 2

Assertion: Physics uses mathematics.

Reason: Mathematics gives precise form to physical laws.

Answer: (a)

Explanation: Both are true and reason explains assertion.

Assertion Reason 3

Assertion: A hypothesis must be testable.

Reason: Untestable statements cannot be verified scientifically.

Answer: (a)

Explanation: Correct scientific reasoning.

Assertion Reason 4

Assertion: Gravity dominates atomic structure.

Reason: Electromagnetic force dominates atoms and chemical bonding.

Answer: (d)

Explanation: Assertion is false because electromagnetic force dominates atomic structure; reason is true.

Assertion Reason 5

Assertion: Electromagnetic force can be repulsive.

Reason: Like charges repel each other.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 6

Assertion: Strong force binds nucleus.

Reason: It acts at nuclear range and overcomes proton repulsion.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 7

Assertion: Weak force causes beta decay.

Reason: Beta decay involves particle transformation.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 8

Assertion: A model has limitations.

Reason: A model is a simplified representation of reality.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 9

Assertion: Accuracy and precision are identical.

Reason: Accuracy means closeness to true value.

Answer: (d)

Explanation: Assertion false, reason true.

Assertion Reason 10

Assertion: Leading zeros are not significant.

Reason: They only locate the decimal point.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 11

Assertion: Doping changes conductivity of a semiconductor.

Reason: Doping changes number of charge carriers.

Answer: (a)

Explanation: Both are true and reason explains assertion.

Assertion Reason 12

Assertion: Physics uses mathematics.

Reason: Mathematics gives precise form to physical laws.

Answer: (a)

Explanation: Both are true and reason explains assertion.

Assertion Reason 13

Assertion: A hypothesis must be testable.

Reason: Untestable statements cannot be verified scientifically.

Answer: (a)

Explanation: Correct scientific reasoning.

Assertion Reason 14

Assertion: Gravity dominates atomic structure.

Reason: Electromagnetic force dominates atoms and chemical bonding.

Answer: (d)

Explanation: Assertion is false because electromagnetic force dominates atomic structure; reason is true.

Assertion Reason 15

Assertion: Electromagnetic force can be repulsive.

Reason: Like charges repel each other.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 16

Assertion: Strong force binds nucleus.

Reason: It acts at nuclear range and overcomes proton repulsion.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 17

Assertion: Weak force causes beta decay.

Reason: Beta decay involves particle transformation.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 18

Assertion: A model has limitations.

Reason: A model is a simplified representation of reality.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 19

Assertion: Accuracy and precision are identical.

Reason: Accuracy means closeness to true value.

Answer: (d)

Explanation: Assertion false, reason true.

Assertion Reason 20

Assertion: Leading zeros are not significant.

Reason: They only locate the decimal point.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 21

Assertion: Doping changes conductivity of a semiconductor.

Reason: Doping changes number of charge carriers.

Answer: (a)

Explanation: Both are true and reason explains assertion.

Assertion Reason 22

Assertion: Physics uses mathematics.

Reason: Mathematics gives precise form to physical laws.

Answer: (a)

Explanation: Both are true and reason explains assertion.

Assertion Reason 23

Assertion: A hypothesis must be testable.

Reason: Untestable statements cannot be verified scientifically.

Answer: (a)

Explanation: Correct scientific reasoning.

Assertion Reason 24

Assertion: Gravity dominates atomic structure.

Reason: Electromagnetic force dominates atoms and chemical bonding.

Answer: (d)

Explanation: Assertion is false because electromagnetic force dominates atomic structure; reason is true.

Assertion Reason 25

Assertion: Electromagnetic force can be repulsive.

Reason: Like charges repel each other.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 26

Assertion: Strong force binds nucleus.

Reason: It acts at nuclear range and overcomes proton repulsion.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 27

Assertion: Weak force causes beta decay.

Reason: Beta decay involves particle transformation.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 28

Assertion: A model has limitations.

Reason: A model is a simplified representation of reality.

Answer: (a)

Explanation: Correct explanation.

Assertion Reason 29

Assertion: Accuracy and precision are identical.

Reason: Accuracy means closeness to true value.

Answer: (d)

Explanation: Assertion false, reason true.

Assertion Reason 30

Assertion: Leading zeros are not significant.

Reason: They only locate the decimal point.

Answer: (a)

Explanation: Correct explanation.

14. Case Study Questions

Case Study: Scientific Method

A student observes that a pendulum takes different times for different lengths. The student forms a hypothesis, changes length, measures time and analyses a graph.

Questions: 1. What is the observation? 2. What is the independent variable? 3. What is the dependent variable? 4. Why repeat readings? 5. What follows if data supports hypothesis?

Answers: Length affects time period; length; time period; to reduce random error; hypothesis may support a theory or law.

Explanation: The passage connects chapter ideas with exam-style reasoning.

Case Study: Fundamental Forces

Four fundamental forces explain physical interactions from nuclei to galaxies. Strong binds nuclei, EM controls atoms, weak causes beta decay and gravity controls astronomy.

Questions: 1. Strongest force? 2. Weakest force? 3. Force in beta decay? 4. Force in chemical bonding? 5. Force in planetary motion?

Answers: Strong nuclear; gravitational; weak nuclear; electromagnetic; gravitational.

Explanation: The passage connects chapter ideas with exam-style reasoning.

Case Study: Models in Physics

The Bohr model explains hydrogen spectrum but fails for many-electron atoms. It is still useful for basic atomic ideas.

Questions: 1. Is it a model? 2. Is it complete? 3. Why useful? 4. What is limitation? 5. What lesson does it teach?

Answers: Yes; no; explains hydrogen; fails for many-electron atoms; models have limited validity.

Explanation: The passage connects chapter ideas with exam-style reasoning.

Case Study: Accuracy and Precision

A group gets readings close to each other but far from accepted value. Another group has scattered readings around accepted value.

Questions: 1. First group precision? 2. First group accuracy? 3. Second group accuracy? 4. Cause of offset? 5. Cause of scatter?

Answers: High precision; low accuracy; may be accurate on average; systematic error; random error.

Explanation: The passage connects chapter ideas with exam-style reasoning.

Case Study: Physics and Technology

Smartphones use semiconductors, waves, optics, sensors and batteries. Medical imaging uses X-rays, MRI and ultrasound.

Questions: 1. Chips use which field? 2. Wireless uses what? 3. Camera uses what? 4. MRI uses what? 5. What is technology?

Answers: Semiconductor physics; electromagnetic waves; optics; magnetic fields and radio waves; application of science.

Explanation: The passage connects chapter ideas with exam-style reasoning.

15. Quick Revision Notes

One-page Summary

Physical World introduces Physics, scientific thinking, scope of science, models, fundamental forces, technology and measurement ideas.

Most Asked Questions

Theory vs law
Accuracy vs precision
Strongest and weakest force
Why models have limitations
Steps of scientific method

Common Mistakes

Calling theory a guess
Confusing accuracy and precision
Saying gravity is strongest
Forgetting leading zeros are not significant

Last-minute points: Physics studies nature. Scientific method is evidence-based. Models are useful but limited. Strong force is strongest, gravity is weakest. EM controls atoms and chemistry. Weak force causes beta decay. Accuracy means true-value closeness; precision means repeatability.