Every topic, every MCQ and every exercise question, explained step by step in simple language. Written for the Punjab Board new-syllabus Physics book, English medium.
On their own page:Chapter 9 MCQsChapter 9 Short QuestionsChapter 9 Long Questions
Read this first. Everything in the exercises comes from these topics.
The collective knowledge about natural phenomena, processes and events occurring around us, gathered by observation and experiment.
| Biological sciences | Physical sciences |
|---|---|
| Study living things | Study non-living things |
| Botany, zoology, microbiology | Physics, chemistry, astronomy, geology |
Physics is an important and basic part of the physical sciences.
The fundamental science that deals with the constituents of the universe, that is matter, energy, space and time, and their mutual relationships and interactions.
| Constituent | Meaning |
|---|---|
| Matter | Anything that has mass and occupies space |
| Energy | The ability to do work |
| Space | The three-dimensional extent in which all objects and events occur; it lets us describe positions and motion |
| Time | Measures the order and duration of events; treated as the fourth dimension |
An effect described by the special theory of relativity: time passes more slowly for an observer moving at ultra-high speed than for one at rest.
Physics tries to understand how the universe works, from the smallest subatomic particles to the largest stars and galaxies.
| Branch | What it studies |
|---|---|
| Mechanics | Motion and the effects that influence it; based on Newton's laws of motion and gravitation (classical mechanics) |
| Heat and thermodynamics | Thermal energy of materials and its flow from one body to another |
| Acoustics | The nature and physical aspects of audible sound |
| Optics | The physical aspects of visible light |
| Electromagnetism | Electric and magnetic effects and the relation between electric current and magnetic field |
| Quantum mechanics | The behaviour of particles at atomic and subatomic level |
| Relativistic mechanics | How space and time depend on the observer, and how speed and gravity affect them |
| Nuclear physics | The properties of the nuclei of atoms |
| Particle physics | Subatomic and elementary particles, the building blocks of matter |
| Astronomy | The distribution of celestial bodies: planets, stars, galaxies |
| Cosmology | The large-scale structure and evolution of the universe |
| Solid state physics | Particular properties of matter in solid form |
The integration and interaction of physics with other fields of study: physics supplies principles, techniques and methods used across many disciplines.
| Field | What it does | Example |
|---|---|---|
| Biophysics | Uses physics to describe biological systems | Mechanics of bones and muscles; physical properties of cells and tissues |
| Medical physics | Physics for diagnosis and treatment | X-rays, ultrasound, MRI, CT scans, radiotherapy for cancer |
| Astrophysics | Physical properties and processes of celestial bodies | How matter and energy interact in stars and space |
| Geophysics | Physics of the Earth | Earth's interior, magnetic and gravitational fields, earthquakes, volcanoes |
| Climate physics | Physical processes of the environment | Atmospheric motion, climate change, weather |
| Computational physics | Computers used to solve complex physics problems | Simulating weather or the motion of galaxies |
A systematic approach used to search for the truth of an issue and to solve problems about the natural and physical world.
| Step | What happens |
|---|---|
| 1. Observation | Recognise a problem and gather information by observing or from experiments |
| 2. Hypothesis | Propose a possible explanation (an educated guess) that can be tested |
| 3. Experiment | Test the hypothesis by an organised, repeatable process; record, organise and analyse the data |
| 4. Theory | A hypothesis that passes careful testing becomes a theory: a logical explanation of causes and effects |
| 5. Prediction | Use the theory to predict unknown results and design new experiments to test them |
| 6. Falsifiability | The theory must make claims that could be shown false by a test |
| 7. Law | A theory that passes many tests and is generally accepted becomes a law |
If results do not agree, the hypothesis is changed or rejected and the cycle runs again. That is why the arrows in the flowchart loop back.
| Step | In this example |
|---|---|
| Observation | An opaque object in the path of light from the Sun or a lamp forms a shadow |
| Hypothesis | Light travels in straight lines, so an opaque object blocks it and leaves a shadow |
| Experiment | Four cardboards with holes are lined up in front of a torch (below) |
| Theory | Light travels in a straight line |
| Prediction | A ball will cast a round shadow and a block a rectangular one |
| Law | Law of rectilinear propagation of light |
The light reaches the screen only when the holes are in a straight line, so the hypothesis is supported.
A possible explanation or educated guess, proposed on the basis of observations, that can be tested by experiment.
A hypothesis that has been verified by careful experiments: a logical explanation of the causes and effects of an event in nature, applicable to similar events.
A theory that has been tested many times and is generally accepted as true: a statement about the behaviour of nature that explains past observations and predicts others.
The idea that a theory is scientific only if it makes claims and predictions that can be tested and could, in principle, be proved wrong.
| Hypothesis | Theory | Law |
|---|---|---|
| An educated guess | A tested explanation | A widely accepted statement |
| Not yet tested | Passed careful tests | Passed tests again and again |
| Explains one observation | Explains a group of events | Describes how nature always behaves |
Science never claims final truth. Theories and laws are man-made ideas; new facts and better experiments can modify or overturn them.
A small amount of data can prove a prediction wrong (one clear failure is enough), but no amount of data proves it always right.
| Term | Meaning | Example |
|---|---|---|
| Science | Collective knowledge about natural phenomena, processes and events | Laws of heat and motion |
| Technology | Methods and techniques developed by using scientific knowledge (machines or software) | Automobile, radar and laser technology |
| Engineering | Applying technologies and scientific principles to design instruments and tools and build things that meet needs | A civil engineer designs a bridge; a software engineer designs a phone app |
| Technology | Based on |
|---|---|
| Automobiles | Thermodynamics (heat into work) |
| Refrigeration and air conditioning | Thermodynamics (moving heat) |
| Radar | Detection and reflection of electromagnetic waves |
| Laser | Atomic physics; used in medicine, metallurgy, industry, telecommunication and space |
| Smartphone apps | Information technology |
Engineers also consider cost and safety when they design a product.
Try each one first: tap an option to check it, then read the reasoning and why the others are wrong.
Only the mcqs on one page →The wording follows published solved exercises and every answer was re-checked by hand, so the wording or the order of options may differ slightly from your print.
The multiple-choice questions at the end of Chapter 9 in your book, in the book's option order.
Physics is a branch of:
Physics, chemistry: physical sciences.
Which branch of science plays a vital role in technology and engineering?
Technology runs on physics.
Automobile technology is based on:
Engines = thermodynamics.
A user-friendly software application of a smartphone uses:
Software = IT.
The working of refrigeration and air conditioning involves:
Heat moved about = thermodynamics.
What is the ultimate truth of a scientific method?
The method ends at a law.
The statement "If I do not study for this test, then I will not get a good grade" is an example of:
"If ... then ..." = prediction.
Which of the following are methods of investigation?
All three gather evidence.
A hypothesis:
Book key: all of these.
A graph of organised data is an example of:
Graph = analysis.
The colour of a door is brown. It is an example of:
Seen and noted = observation.
Extra questions on the same ideas, of the kind set in board papers and class tests.
Physics deals with matter, energy, space and time, and:
Matter, energy, space, time and how they interact.
According to the special theory of relativity, for an observer moving at a very high speed, time:
Fast mover, slow clock.
The branch of physics that deals with the nature and physical aspects of audible sound is:
Acoustics = sound.
The behaviour of particles at the atomic and subatomic level is explained by:
Tiny particles = quantum.
The branch that explores the large-scale structure and evolution of the universe is:
Cosmos = universe.
X-rays, ultrasound, MRI and CT scans belong to the interdisciplinary field of:
Hospital physics = medical physics.
Earthquakes, volcanoes and the Earth's magnetic field are studied in:
Geo = Earth.
The first step of the scientific method is:
First look, then guess.
An organised, repeatable process used to test the truth of a hypothesis is called:
Test = experiment.
A theory is called scientific only if it makes predictions that can be tested and could be proved wrong. This idea is called:
Falsifiable = could be shown false.
If repeated tests of a prediction do not agree with the theory, the scientist should:
Evidence wins.
Radar technology is based on:
Radar: EM waves. Laser: atomic physics. Car: thermodynamics.
Designing a bridge that can withstand strong winds, earthquakes and heavy traffic is the work of:
Civil = structures.
Exam-ready answers. Learn the meaning, then write them in your own words.
Only the short questions on one page →The knowledge about natural phenomena, processes and events around us, gained by observation and experiment.
The fundamental science of the constituents of the universe (matter, energy, space and time) and their mutual relationships and interactions.
Branches: mechanics, heat and thermodynamics, acoustics, optics, electromagnetism, quantum mechanics, relativistic mechanics, nuclear physics, particle physics, astronomy, cosmology, solid state physics.
Fields formed by the integration and interaction of physics with other subjects, where the principles and methods of physics are applied to them.
Examples: biophysics, medical physics, astrophysics, geophysics, climate physics, computational physics.
A possible explanation or educated guess proposed on the basis of observations, which can be tested by experiment.
Example: shadows of opaque objects are formed because light travels in straight lines.
| Theory | Law |
|---|---|
| A hypothesis verified by careful experiments | A theory tested many times and generally accepted as true |
| A logical explanation of the causes and effects of an event | A statement of how nature behaves, explaining the past and predicting the future |
| Example: light travels in straight lines | Example: law of rectilinear propagation of light |
Laser technology is based on the principles of atomic physics. It is used in medical diagnosis and treatment, metallurgy, industry, telecommunication and space exploration.
A theory is scientific only if it makes claims and predictions that can be tested and could possibly be proved false.
Importance: it keeps science free of vague or untestable claims, and separates real scientific theories from beliefs that can never be checked by experiment.
These test whether you really understand. Give a reason every time.
No. Scientific theories and laws are man-made ideas about how nature works. They are accepted because the evidence so far supports them, but future discoveries can bring new facts that make us modify or reject them.
Example: Newton's laws of motion were thought complete, but at speeds close to that of light they had to be corrected by the theory of relativity.
Yes, they may. Laws are based on the evidence available today. Better instruments and new experiments keep bringing fresh facts; if a law fails to explain them, it is modified or replaced. For example, Newton's mechanics still works for everyday speeds but was extended by relativity for very high speeds and by quantum mechanics for atoms.
Doctors, medical physicists, electricians and pilots also use scientific knowledge every day.
A theory is used to make predictions, and experiments are designed to test them again and again. If the results repeatedly disagree with the predictions, or new facts appear that the theory cannot explain, the theory is modified; if it cannot be fixed, it is rejected and a new hypothesis is made.
The statement is correct. This is the idea of falsifiability. A scientific theory must make clear predictions that a test could show to be false. A claim that no experiment could ever contradict cannot be checked, so it is not science, however true it sounds.
New ideas that challenge accepted "truths" have usually been met first with doubt and resistance. Scientists ask for strong evidence before giving up a well-tested idea; this caution is part of science. When the new evidence is repeated and confirmed, the old idea is modified or replaced, as when the Sun-centred model replaced the Earth-centred one.
Not necessarily wrong, but it is unscientific. If no observation or experiment can test it, it can be neither supported nor disproved by evidence, so it lies outside science. A scientific hypothesis must be testable.
Agreeing results only show that the prediction worked in the cases tested; there may always be a case not yet tested where it fails. But a single reliable result that disagrees is enough to show that the prediction is not always true.
Example: seeing a thousand white swans cannot prove that "all swans are white", but seeing one black swan proves that statement false.
A hypothesis is a proposed explanation; an experiment is an organised, repeatable process designed to test it. If the experimental evidence supports the hypothesis, it can become a theory; if not, the hypothesis is changed or rejected.
Problems such as climate change, disease prevention and treatment, and sustainable energy have many sides: physical, chemical, biological, economic and social. No single subject has all the knowledge needed. Working together, experts combine their methods and points of view, which leads to new ideas and quicker, better solutions.
Long answers, explained in full with headings. Learn the structure: definition, explanation, diagram or table, example.
Only the long questions on one page →The long questions at the end of the chapter in your book.
The interdisciplinary nature of physics is the integration and interaction of physics with other fields of study. Physics provides principles, techniques and methods that are used in many other subjects, creating new fields.
Describes biological systems and processes with the principles and techniques of physics. Example: the mechanics of bones, muscles and other biological structures; physical properties of cells, tissues and organs.
Applies physics to develop techniques for diagnosis and treatment. Example: X-rays, ultrasound, MRI and CT scans; radiation therapy for cancer.
Studies the physical properties and processes of celestial bodies. Example: how matter and energy interact in stars and space, to understand the universe as a whole.
A systematic approach used to search for the truth of an issue and to solve problems about the natural and physical world.
Observe a natural process and collect information. Example: an opaque object in sunlight or lamplight casts a shadow.
A possible explanation that can be tested. Example: light travels in straight lines, so an opaque object blocks it and a shadow forms.
An organised, repeatable test of the hypothesis. Example: with the holes of four cardboards in line, the torch light passes through all of them; moving one card blocks it.
The tested hypothesis becomes a theory explaining causes and effects. Example: light travels in a straight line.
The theory predicts new results. Example: a ball will cast a round shadow and a block a rectangular one.
The predictions must be testable and capable of being proved wrong; if tests disagree, the hypothesis is changed or rejected.
After many successful tests and wide acceptance, the theory becomes a law. Example: the law of rectilinear propagation of light.
The collective knowledge about natural phenomena, processes and events around us. Example: the laws of thermodynamics; knowing that electromagnetic waves reflect from objects.
The methods and techniques developed by using scientific knowledge; it may be a machine or a software programme. Examples: automobile technology (thermodynamics), radar technology (reflection of electromagnetic waves), laser technology (atomic physics).
The process of applying technologies and scientific principles to design instruments and tools and to build things that meet specific needs, keeping cost and safety in mind. Examples: a civil engineer designs a bridge; a software engineer designs a smartphone app; an aviation engineer designs an aircraft.
| Science | Technology | Engineering | |
|---|---|---|---|
| Is | knowledge | methods and techniques | design and building |
| Asks | why and how? | how can we use it? | how do we build it? |
| Example | laws of heat | car engine technology | designing a car |
Physics studies matter, energy, space and time and how they interact, from subatomic particles to galaxies. Its laws are behind almost every machine and device we use, so it is the core of technology and engineering.
| In daily life | Physics behind it |
|---|---|
| Cars and motorbikes | Thermodynamics: fuel's heat turned into motion |
| Refrigerators and air conditioners | Thermodynamics: heat moved out |
| Radar at airports | Reflection of electromagnetic waves |
| Laser surgery, barcode readers, fibre-optic internet | Atomic physics (lasers) |
| Mobile phones | Electromagnetism, electronics and information technology |
| X-rays, ultrasound, MRI | Medical physics |
| Electricity at home | Electromagnetism (generators, transformers) |
Physics is also used in metallurgy, industry, telecommunication and space exploration.
Long questions often set in board papers from this chapter, answered in the same full style.
A possible, testable explanation proposed on the basis of observations.
A hypothesis verified by careful experiments; a logical explanation of causes and effects.
A theory tested many times and generally accepted as true.
| Hypothesis | Theory | Law |
|---|---|---|
| guess | tested explanation | accepted statement |
| may be rejected | may be modified | may still be revised by new evidence |
A theory is scientific only if it makes claims and predictions that can be tested and could possibly be proved false.
Many agreeing results cannot prove that a prediction is always true, but one reliable disagreeing result proves that it is not.
"Light travels in straight lines" is falsifiable: if light reached the screen through four holes that were not in line, the idea would be shown false. It has never failed such a test, so it is accepted as a law. A claim like "invisible spirits cause shadows, but can never be detected" cannot be tested at all, so it is not scientific.
Interdisciplinary research brings experts from different subjects together, so that the methods of physics, chemistry, biology, computing and other fields are used on one problem.
Technology is the use of scientific knowledge to develop methods and machines. Physics is at its core, because almost every invention is based on physical laws and principles.
Based on thermodynamics: the engine burns fuel and turns thermal energy into mechanical work that drives the wheels. Refrigeration and air conditioning are also based on thermodynamics.
Based on the detection and reflection of electromagnetic waves: radio waves sent out are reflected by aircraft, ships or storms, and the echo shows their distance and speed.
Based on the principles of atomic physics. Lasers are used in medical diagnosis and treatment (eye surgery), metallurgy (cutting and welding), industry, telecommunication (optical fibres) and space exploration.
Smartphones and their user-friendly apps combine electronics and software designed by software engineers.
Use this the night before the test.
Biological sciences and physical sciences
Matter, energy, space and time
Time passing more slowly for an observer moving at very high speed
Nuclear physics
Optics
Medical physics
Observation
A hypothesis
It is changed or rejected
It cannot be tested or proved wrong (not falsifiable)
Atomic physics
A civil engineer
Climate change (or disease, sustainable energy)
No, but one disagreeing result can prove it is not always right
Give yourself 25 minutes. Pick one option for each question, then submit to see your score and which questions to revise. Any question you get wrong tells you which topic to read again.
