2024 A-level Physics Live Q&A ?

Hi everyone, similar to last year, I'll be opening up this Alevel'24 Q&A group to all JC students who would like to clarify any questions or gain clarity on certain concepts you've learnt in school.

I will try to host some live Q&A calls where I would help answer any question you have. You may also send questions you have into this group and I will help to answer them.

Do join the group using the link below. Hope this helps with your revision!

https://t.me/ThePhysicsPageAlvlQnA

ThePhysicsPage_

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🤯 ThePhysicsPage A-level Q&A 2024

Welcome, do PM me (or send into this group) any questions you have. It will be great if you can be specific in your doubts, though I understand that it may be hard to provide specifics if you are totally confused.

*? What is the direction of friction on the wheels of a car / bicycle? ?***

A very common confusion that many O-level students have is regarding the direction of friction on the wheels of a bicycle/car.

Here is a concise summary:

Driving Wheels (powered by the engine or pedals):
- Friction acts forward relative to the motion of the vehicle.
Explanation: For both cars and bicycles, the friction force on the driving wheels (the wheels that are powered by the engine or pedals) acts forward relative to the motion of the vehicle. This is because the engine or pedals push the wheel backward against the ground, and friction opposes this motion by pushing the vehicle forward.

Non-Driving Wheels (free-rolling):
- Friction acts backward relative to the motion of the vehicle.
Explanation: For the non-driving wheels (those that are not powered), friction acts backward relative to the motion of the vehicle. This friction force opposes the tendency of the wheels to slide forward due to the vehicle's motion.

For those who need a more visual understanding of things or want some practice questions, check out this link for a good infographic created by Evan's Space.
https://evantoh23.wordpress.com/2022/10/20/direction-of-friction-on-the-wheel/

ThePhysicsPage_ ??

Evan's Space

Direction of friction on the wheel

There have been a few questions in Olevel asking students the direction of the friction on the wheel, It is important to consider if the wheel is connected to the engine or not. Below is an illustr…

Resources for Understanding Superposition ?
A common problem that students face with this topic is understanding the difference between the different experiments in superposition. I have attached two links which have helped in my understanding of this topic.

The first video provides an overview of the difference between the three experiments.
?https://youtu.be/Z9jv23Pa_3E?feature=shared

The second provides an explanation and visual demonstration of how the double slit pattern should look like when we account for the single-slit pattern envelope. This second video was crucial in helping me better understand what this "single slit envelope" was all about.
?https://youtu.be/k18tDUFD5iY?feature=shared
*⚠️ Do share this with others who may be struggling with this topic. T*his is a tricky topic for most, and I will continue to send more resources to help in the understanding of this topic.

ThePhysicsPage_ ??

The topic "Light" is mainly split into 3 parts: Reflection, Refraction, Lenses.
A common testing point in all of these parts are ray diagrams. As such, it is important for you to practice drawing all the different diagrams ahead of the exam.

Ray Diagrams To Master: ??
1. Mirror Diagrams for Reflection
2.Refraction of light ray diagrams (more dense-less dense, less dense-more dense, critical angle)
3. Lenses

When practicing ray diagrams, there are a few things to note:
a. Direction of arrows (Arrows should always be directed into the observer's eye! If you draw arrows coming out of the eye, you are implying that our eye emits light)
b. Dotted/Bold lines (Dotted lines are for light rays that are behind the mirror (i.e., virtual plane)
c. Orientation/size of the image (for different case, the image produced may be bigger, smaller, or inverted)

Paying attention to these points will help in your practice.

Part 1: Reflection ?
Apart from ray diagrams, the other concept to know for reflection is that the angle of incidence is equal to the angle of reflection.

Part 2: Refraction ?
a. First, you should understand that light rays bend because of the change in speed of light when travelling in different mediums.
b. Next, you will need to pay attention to whether light rays bend away/towards the normal (this depends on what medium the light is travelling towards).
c. Know the formulas for refractive index:
(i) n1sin(i) = n2sin(r) where n1, and n2, are the refractive indexes in mediums 1 and 2 respectively
(ii) n = c/v where c is the speed of light in vacuum and v is the speed of light in the medium
d. Know the conditions for critical angle and how to calculate it

Part 3: Lenses ?
a. The main thing that students struggle with is drawing the different lens diagrams. This, however, requires practice and some memorisation of the different scenarios. I would suggest spending time sitting down and practicing all the different scenarios and commit them to memory
b. Along with the ray diagrams, you should also know the applications of the different lens scenarios

Final notes:
For those struggling with light, I find that this website has some good notes and practices for this topic: https://evantoh23.wordpress.com/

Do forward this post to those who may benefit from it! ?
As always, if you need help please do drop a message to me or in our discussions group.

Hope this helps,
ThePhysicsPage ??

?For O-levels, light is a common topic which some may find difficult. Since the question asked is not specific to any particular concept, I will try to give you a broad overview of what you need to know to grasp this topic. If you have any specific questions about this topic, please do let me know.

[Part 1]
Here are some things which you can implement in your study schedule which will make a difference to your physics revision (I will start from basic changes to your study technique to more detailed physics tips)

1. Analyse your study schedule ?
At this point I'm time, you should take a look at your different subjects and start prioritising. Ask yourself: Based on your grades (and your level of confidence) which subject deserve more time? Do not just base your decision on your grades. Sometimes, the subject you have the highest grade in that exam may be the one which you are least confident. What I did was to allocate the time I should spend on each subject for the whole week. From there, I will then know how many hours I should spend on the subject when I plan my time each day. If you are struggling equally with all your subjects, don't worry, the key is that you recognise this and ensure you give equal attention to all your subjects.

If you do not have the habit of planning your day, you should start to plan it out! I strongly believe in this technique of time blocking - you can search more about this, or maybe I'll explain more about this technique soon.

2. Implement active reviewing into your study schedule. ?
I have went in depth into this study method which I used in JC. Do check out these posts:
Reviewing
Reviewing pt. 2
This technique will significantly change how you absorb what is taught in school and I assure you, you will see results if you do it correctly.

3. Reflect on your struggles ?
Many students feel that they are not good at physics. I urge you to reflect on some of these questions below as it will shed some light on what you need to work on.
a. Are you struggling with understanding the content? (Some signs would be if you're confused with what is being taught in class, or when you see a question, you do not know what are they asking/testing you)

b. Are you struggling with applying your knowledge to physics questions? (Some signs may be, you understand what is taught in the lecture and in your notes. But when you solve a question, you are not sure how those content links to the context of the question. Upon seeing the solutions, you understand what is being done)

c. Are you someone that can do the calculations but can't answer structured questions?

d. Time management in exams
(This is unlikely your problem given the way your question is asked, but some students may still fall into this category)

Look at the questions above and ask yourself which category do you fall into? You may find yourself in more than one category, that's okay.

For those in category A, it is important that you re-learn/re-read your lecture notes to understand the relevant content. You should consult your teachers/tutors to help with your content understanding. To improve your content mastery, do not just read through the notes. If you find certain parts hard to understand, think of what specifically confuses you and frame your question in a way that answers that doubt. Many students just ask their teachers questions like "I don't understand this". This doesn't help in your learning. Instead you should ask specific questions that will allow your teacher to understand what you are thinking.

Those in category B, you should practice questions related to topics that you struggle with. I talk about this quite extensively in this post: approaching practice papers. Do check it out.

Hi, thanks for this question! It can be daunting trying to revise when we do not know where/how to start (especially when we still have to constantly learn new topics). I will try to share some tips which I believe will help in your revision! (these need not apply only to h2 physics)

The topic of superposition is mainly split into the following parts:

1. Understanding interference and diffraction in its general sense. ?
What I mean by this is that students need to understand how interference comes about and how you get constructive/destructive interference (e.g., nλ path difference for constructive interference - assuming sources are in phase). To understand this, you will not need to be bothered with the 3 major setups (young's double slit, diffraction, single slit) that you will see in this topic. You just need to understand the principle of interference and diffraction - these phenomena can happen anywhere. A common misconception is that interference can only happen in those 3 experiments. That is not true.

2. Understanding Standing Waves ??‍♂️
The next part that you need to know is how standing waves are formed, the different harmonics given different constraints (open-closed, open-open, closed-closed). These are one category of common questions that can be tested as an mcq or a structured question.

3. Understanding the 3 Major Experiments ?
Young's Double Slit, Diffraction Grating, Single Slit. These 3 experiments may be confusing to some. It is helpful to take time understanding how these equations are derived. But don't get too caught up with the derivation. The understanding is important. Once you understood it, just take the formula as given and apply it. Many students keep worrying about how the formulas for different setups are derived. While this would help in your understanding, the derivation is often meaningless when solving questions.
If you loo closely, the formula for all the 3 experiments take on the same form - dsinθ = nλ. The only difference is that the symbols mean different things in each of the experiments. For example "n" in a double slit experiment represents the first maxima while for the single slit experiment, 'n' represents the first minima. Hence, it is important to know these differences.

4. Single-slit Envelope and Rayleigh Criterion ?
The final part of this topic is understanding that the single slit pattern will envelope the double slit pattern and hence in your double slit experiment, the observed intensity on the screen would be "limited" by the single slit envelop. Additionally, questions involving superposition usually have one question relating to the resolution of the images (these require you to apply Rayleigh's criteria).

If you do focused practice on questions relating to the different parts of this topic (and of course, ensure that you learn from these practices), you will be able to gain a good grasp of the topic of superposition as a whole! Do reach out to me if you need more help or clarification - you can also ask another question in the same link provided!

*❗️Do share this with your friends who may be similarly struggling with this topic!*

ThePhysicsPage_ ??

Superposition... one of the topic that frustrates people the most! The question you ask seems like a general question about this topic so i'll give some advice on how i studied for this (do ask again if you have any specific questions about the topic)