What to Expect at Different Levels of Physics

So you’ve got interested in physics and now want to learn it properly.

I would like to start with the fact that there is no age to start learning physics. But just going by the general school curriculum: basic physics in grade 5,6,7 and sometimes grade 8 are classified under the subject of “Science” along with Biology and Chemistry. And it’s only in grade 9 that the science subjects bifurcate and you have physics, chemistry and biology as separate subjects. You might also notice that based on the school, the board, the curriculum etc. that the level of physics taught to you may be easier or tougher than the ones taught to your friends of the same age group but different school, college or board. Nevertheless, the physics is same for everyone and it’s just a matter of what depth the topic is covered in and which topics does each of you have. This post is for those you are just getting started in physics, mainly high schoolers. It’s a common trend that those who have completed grade 12 physics basically know what to expect from the subject and how to navigate around in terms of books to refer to or the mathematics they may need to learn.

This post is for Level 1 physics. I will make a similar one for higher levels in the future and link them here.

Level 1 (Grade 9 -10, Secondary School)

Your textbooks are your best place to start.

In many schools grade 9 and 10 usually go together followed by a final board exam. So for obvious reasons grade 9 would have easier topics. And the topics get more challenging as you go through your grades but this is not always the case for all topics. The main reason is because physics can be categorized and classified into different subfields and one field might have a different approach compared to others. For example the topic on light falls under the category of optics or optical physics but at this grade level it is only geometric in nature. However the topic on motion has graphs and algebraic equations.

The main categories you will cover in grade 9 and 10 are:
(you can click on the topic name to skip to that particular topic directly)
– Measurements
– Force and Motion
– Scalars and Vectors
– Energy, Power and Efficiency
– Thermal Physics
– Waves
– Light Rays and EM Waves
– Electricity and Magnetism
– Atomic and Nuclear Physics

Measurements

Start with Measurements. While measurements is the first chapter in practically every physics text book, you need to think of measurements as a part of every single topic. Here you will be introduced to what physical units are and how some of them are defined. You will understand what are 7 basic physical quantity and what are the derived physical quantities. You will mostly be introduced to what the S.I. units are and how to use the scientific notation to represent physical quantities.

Classification:
Measurements fall under the category of Metrology which is the scientific study of Measurements (not to be confused with Meteorology which is the scientific study of atmosphere and weather)

What Next?:
The next level will be encountered in grade 11 and will cover Uncertainties and Errors and more importantly how to calculate errors (the bedrock of all physics)

Force and Motion

The next easiest topic to move onto is Motion of objects. This topics comes as a pair: Motion and Forces. At this grade level the topic is mainly used to introduce a few major concepts. The main one being acceleration is not velocity. Since most student would be doing this for the first time in their life. You will mainly be working under these constraints: All motion will be 1 dimensional. That means the objects that you are studying are either moving either horizontally or vertically. Further, if it’s horizontal its mostly moving only to the right or only to the left and similarly for vertical motion it’s moving either just up or just down. When it comes to acceleration it’s mostly 0 m/s² and if it’s not zero, then it’s constant and you would be concerned about only how the velocity changes due to acceleration.
Force is what causes acceleration which in turn creates various motions. The second part deals with Newtons 3 laws of motion. For this level you will mainly focus on the second law, that gives the equation F = ma
Technically in order to do mechanics you need to know how to work with vectors. But with the constraints mentioned above you don’t need to know vectors before starting this topic.
You may also be introduced to Torque and rotational equilibrium and concepts of Center of mass as well.

Classification:
Force and Motion Falls under the category of Mechanics and more specifically Classical Mechanics. Mechanics is the study of how objects move and interact with each other and most of it was developed by Galileo, Newton with the help of many before them. So what you are learning is what was developed in year 1600 and before. In the later years it was further refined.

What Next?
The next level you will encounter in grade 11. and in grade 11 you will be using your full knowledge of Vector Algebra to handle this topic. Unlike grade 9-10 where motion is just moving to the right or left, in grade 11 you will deal with projectile and circular motion where the object is moving in 2 dimension along a curve.

Scalars and Vectors

Strictly speaking. Scalars and Vectors is mathematics and not exactly physics. It has a wide range of application but the way you will learn it in grade 9-10 would be: What are scalars and vectors?, What’s the difference between them? and How do you add and subtract them in 2 dimension (using geometry). You will understand the general idea that to define some physical quantities you will need 3 information: a. the magnitude, b. the physical unit, c. the direction. In that sense Scalars and Vectors are just maths applied to solving physics problems and in higher level physics this will make your life so much easier.

Classification:
Scalars and Vectors fall under the category of Mathematical Physics. When you do physics you will soon realize that maths and physics are very closely intertwined and you can’t really do physics without the maths. Going forward you will also learn calculus. In the previous topic of Forces and Motion you will work on distance-time and speed-time graphs. Though it is not explicitly mentioned it is a precursor of calculus. More advanced problems on speed and distance-time graphs will make intuitive sense of why we need calculus.

What Next?
Going forward you will learn Vectors and scalars in 3dimensions, generalized trigonometry (what is sin, cos and tan of angles over 90^o) Calculus, Matrices, Logarithms, Statistics and Numerical Methods and these are just in grade 11 and 12. Not all of these are covered under physics, some topics like matrices are covered under maths, but they are very useful for physics in almost all areas.

Energy, Power and Efficiency

Energy and Efficiency in grade 9-10 is a simple topic and most students will already be aware of the concepts by this point. The new addition now is that you will learn to quantify energy. And use physics formulas for calculating energy like Kinetic and Potential Energy of objects. The reason why these three topics are clubbed together is because of their similarity and usage. Energy is used in static situations where the energy content of the system is constant before and after a change, like gravitational potential energy before an object starts falling or after it reaches the ground. But in systems like electricity and vehicles, the amount of energy converted depends on how long the machine is switched on for and that’s why power is a more useful quantity to understand and use. As an analogy (which I hate to use), if I had to ask will a car that travels at 80 kmph cover more distance than a human walking at 5 kmph? This question is meaningless without knowing how long did each one move for. All you know is that one moves faster than the other.
The reason why efficiency is covered is due to imperfect system in real life systems. Where there is always energy lost usually in the form of heat loss and not utilized for the intended purpose.

Classification:
Energy, Power and Efficiency fall under the category of Mechanics. It won’t be evident at this level but you can analyze any system in motion as vectors or scalars. While Forces and Motion takes the Vector approach. Energy and Efficiency takes the Scalar approach. This is extremely convenient in many cases because of the Law of Conservation of Energy. The fact that energy cannot be created or destroyed is a useful tool to use in physics.

What Next?
While you use the formulas for calculation Kinetic and potential energy in grade 9-10. Once you know calculus you will learn to create these formulas from scratch. They won’t be something to memorize and you can then use these techniques to create formulas for any type of energy by applying calculus to other areas of physics that you will learn.

Thermal Physics

Thermal physics as the name suggests is all about heat. You will mainly learn the different ways in which heat transfers from one point to another and understand heat energy due to motion and interaction of atoms and molecules. You will also look in to states of matter as interaction at atomic level and learn about various types of heat capacities. The major concept to learn here is that Heat and Temperature are two different physical quantities. You can increase the heat energy of the substance without increasing its temperature. You might also be introduced to at least 2 gas laws. These Gas Laws were discovered experimentally and relates quantities like pressure, temperature and volume of the container for a particular gas and for a particular amount of gas. It’s a fairly simple topic but don’t let the simplicity fool you. This topic lays the foundation of two major fields in physics for the future.

Classification:
Thermal Physics fall under the category of Thermodynamics and Statistical Mechanics. Statistical Mechanics is just the field of Statistics used on Mechanics. It is just a mathematical way of making sense of what we observe based on how we think how billions and billions of individual atoms interact. And thermodynamics is just properties of heat and heat flow. There is a good deal of overlap between thermodynamics in physics and thermodynamics in chemistry. So it should not be surprising to see concepts and topics from chemistry, over here as well.

What Next?
Thermodynamics takes a really intense turn in grade 12, when it comes back as the topic called “Kinetic Theory of Gas”. Here you will apply everything you’ve learnt in Forces and Motion to collision of particles of gas and then come up with various ways to relate heat energy and temperature with volume, pressure and number of particles in the container and in doing so give a theoretical foundation for Gas Laws.

Waves

The person who contributed to physics (specifically mechanics) the most, was Newton. And Newton soon realized that most of nature could be explained if you consider them to be made of particles that are in motion and affected by Force. But it soon made sense to study the phenomenon of waves separately. Unlike particles and solid object that are concentrated and localized, waves are continuous and spread as they move and unlike particles can pass through each other instead of colliding. This topic has the bare minimum. It introduces you to what longitudinal and traverse waves are. And you will learn the properties and characteristics of waves.

Classification:
Waves fall under the category of Wave Mechanics. This is usually a part of Classical Mechanics but given it’s own status. Wave Mechanics deals with describing waves with equations and understanding how do properties of material and medium though which the wave travel affect the wave. In modern physics Quantum Mechanics deals with everything as though they are waves and so sometimes Quantum Mechanics are casually referred to wave mechanics. Wave mechanics also deal with periodic motion and resonance.

What Next?
You will encounter Waves mechanics in grade 11 next. Here you will mostly focus on 1 dimensional wave like a wave on a string. You will start from simple oscillations and then go on to develop the maths to describe a 1-D wave. You would need basic trigonometry and calculus for this topic.

Light Rays and EM waves

Most of you will recognize this as the topic that has Light Rays and Lens Diagrams. This would not be the first time you will be encountering light as you already may have done spherical mirrors, concave and convex mirrors in lower grades. This topic will deal with laws of reflection and refraction, followed by an understanding of what lens are and how to draw ray diagrams for lens. There will also be a small part on the Electromagnetic spectrum and the uses of different types of EM waves. The main highlight of this topic is Snell’s law of refraction and the phenomenon of Total Internal Reflection.

Classification:
Light Rays and EM waves fall under the category of Light and Optics. As innocent as this topic may look the topic of light, it’s properties and uses are extensive and practically affects every part of your life. From the spectacles you wear, to the polarizer on you computer screen, to the laser in your mouse. This sub-field of physics has vast implication in our life. Yet, I personally feel it’s underrated and not covered in as much depth as it should be.

What Next?
In grade 11 or 12 you will learn about properties of light such as Interference, Diffraction and Polarization. Technically these are properties of waves, but since light is a (transverse) wave it inherits these properties. You will be use the wave equations you built and apply it to light waves. There is a debate in physics as to whether light is a particle or wave, but till the end of grade 12 you will work under the classical assumption that light is a wave. And there’s a lot to cover.

Electricity and Magnetism

The magnetism part is fairly straight forward since it would be something that you may have already learnt in lower grades. Now in grade 9-10 you will mainly deal with Ohm’s law and series and parallel circuit in Electricity. Followed by how how flowing electricity creates a magnetic field. Other topics covered are working of a DC motor and AC generator. The biggest and most applicable concept in context of Electromagnetism is called Fleming’s right and left hand rules, which is also something you will become familiar with.
Electromagnetism usually come in a set of 5 topics at every level of physics with increasing complexity at different levels:
a. Static Electricity (only charges and charges are not moving)
b. Current Electricity (here you have a power supply, usually a battery and you study the flow of current through a closed circuit)
c. Magnetism (the properties of magnets)
d. Magnetic Effect of Electric Current (Flowing electricity creates magnetic fields and changing magnetic field produce electricity)
e. Electromagnetic Waves (How interplay of changing fields create EM waves)
The last point of Electromagnetic waves are covered under the topic of Light.

Classification:
Electricity and Magnetism fall under the category of Electro-Dynamics. This is a whole subject on its own and deals with everything electricity and magnetism. A full understanding of Electromagnetism at a higher level needs maths and not just your garden variety maths. Personally I’ve observed from my experience, it is one of those field in physics that uses a host of different mathematics. It will also appear as an add-on to every other field in physics, simply because everything has positive and negative charge.

What Next?
Electricity and Magnetism comes as a full set of the 5 subtopics in grade 11-12. But here you will only be dealing with 1 dimensional electromagnetism. The history of development of Electromagnetism is short and rich. So this makes Electromagnetism not only have a peculiar approach to defining nature, but it’s also the most robust theory in physics out there. Fun Fact: Electromagnetism led to the development of special theory of relativity, but to understand how you need to have a close look at the the theory as it was developed in 3 dimension (that’s undergrad physics). It is also the only theory I know of that has been compatible with both Quantum Mechanics and Relativity.

Atomic and Nuclear Physics

There’s so much in this particular topic that the amount of stuff in grade 9-10 just doesn’t do justice. But to be fair in order to appreciate the inner depths of this topics you would really need to be comfy with advanced physics. In grade 9-10 however, you have bare minimum basics about the structure of atoms and nucleus. The topic also introduces to the concept of nuclear radiation and radioactive decay. It also touches upon nuclear reactions both fission and fusion and safety and hazards of radioactivity.

Classification:
Atomic and Nuclear Physics are categorized under Modern Physics. However if you are interested in physics and proceed to go on further and pursue it. You’ll soon encounter Quantum Mechanics (QM) at some point. And once you have a good grip on QM you will apply the theory to various phenomenon in nature. Two of the places where QM is applied are the structure of atoms and the Nucleus of atoms and each has it own body of knowledge. These are categories in itself and are called Atomic Physics and Nuclear and High Energy Particle Physics

That’s all I have for now. Feel free to comment and add your views and experiences regarding this topic.
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