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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
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2s the making of modern britain, 1951-2007
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Physics
8 Dec 2025
211
5 pages
Nikolay @nikolay
Nuclear physics explores the fascinating world inside atoms, where tiny particles can pack enormous energy and some nuclei... Show more
Nuclear physics starts with understanding what's actually inside an atom's nucleus. An alpha particle is essentially a helium nucleus containing 2 protons and 2 neutrons, which you'll see written as ₄²α in nuclear equations.
Rutherford's gold leaf experiment was the groundbreaking investigation that first revealed the nuclear structure of atoms. This experiment showed that atoms aren't just "plum puddings" of charge, but have dense, tiny nuclei at their centres.
Key Insight The nucleus is incredibly small compared to the whole atom, yet contains nearly all the atom's mass.
This experiment laid the foundation for our modern understanding of atomic structure and nuclear physics.
You can actually measure how big a nucleus is by firing high-energy electrons at it and watching the diffraction pattern that forms. When electrons hit the nucleus, they create circular patterns with dark spots called minima.
The key formula for nuclear radius is R = A₀A^(1/3), where A₀ ≈ 1.4 fm (femtometres) and A is the mass number. This tells us that bigger nuclei aren't just scaled-up versions of smaller ones.
Here's how the maths works if you fire 300 MeV electrons and get your first minimum at 30°, you can calculate the wavelength using E = hf = hc/λ. Then use R = 1.22λ/(2sinθ) to find the nuclear radius.
Pro Tip Remember that E = hf works for particles too, not just photons - this is crucial for electron diffraction calculations.
Some nuclei are naturally unstable and will spontaneously break apart to become more stable. Think of it like a wobbly chair that eventually tips over - it's inevitable, but you can't predict exactly when.
Nuclear instability happens for several reasons too many or too few neutrons, or simply too much energy packed into the nucleus. When nuclei decay, they release particles or energy to reach a more stable state.
This process creates ionising radiation - radiation powerful enough to knock electrons off atoms and damage living tissue. The decay rate decreases over time, but each individual decay is completely random and spontaneous.
Remember Radioactive decay is like popcorn popping - you know roughly how long the whole process takes, but you can't predict which kernel pops next.
There are four main types of nuclear radiation, each with different properties and dangers. Alpha particles (α) are heavy helium nuclei with +2 charge - they're slow but highly ionising and easily stopped by paper or skin.
Beta particles come in two flavours beta-minus (β⁻) are electrons, while beta-plus (β⁺) are positrons. Both are much faster than alpha particles and can penetrate several millimetres of aluminium.
Gamma rays (γ) are electromagnetic waves with no mass or charge. They travel at the speed of light and can penetrate deep into materials - you need thick lead or concrete to stop them.
Safety Alert Alpha particles are most dangerous when ingested because they cause massive internal damage, while gamma rays can harm you from a distance.
The penetrating power increases dramatically paper stops alpha, aluminium stops beta, but only dense materials like lead can stop gamma radiation effectively.
Protecting yourself from radiation exposure follows three simple principles time, distance, and shielding. Spend less time near sources, stay further away, and put barriers between you and the radiation.
The inverse square law explains why distance is so effective I = k/x². This means if you double your distance from a radiation source, the intensity drops to just one-quarter of its original value.
This law works perfectly for gamma rays and applies to alpha and beta particles too, but only in a vacuum. In air, alpha and beta particles lose energy through collisions, so they don't travel as far.
Real-world Application This is why nuclear workers use long-handled tools and work behind thick shields - small increases in distance provide huge safety benefits.
Remember that gamma radiation spreads in all directions from its source, making the inverse square law particularly important for calculating safe working distances.
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the mechanisms of particle interactions through exchange particles and Feynman diagrams. This summary covers key concepts such as beta decay, fundamental forces, and the role of bosons in particle physics, essential for exam preparation.
PhysicsExplore detailed notes covering essential A-Level Physics concepts, including stellar luminosity, electromagnetic radiation, nuclear decay, and gas laws. This resource is designed for AQA and other exam boards, featuring interactive flashcard-style navigation for effective revision. Access the full notes here: https://www.notion.so/Physics-Revision-AQA-A-Level-a87264d9f28c4302b.
PhysicsComprehensive revision notes on Thermal Physics, including key concepts such as phase changes, specific latent heat, the ideal gas law, and the first law of thermodynamics. Ideal for AQA A Level Physics students preparing for exams, with practice questions included to enhance understanding.
PhysicsExplore essential Feynman Diagrams for AQA A Level Physics, covering proton-proton collisions, electron interactions, and beta decay processes. This summary provides a clear understanding of subatomic particle interactions and nuclear equations, crucial for mastering Unit 2: Particles and Radiation.
PhysicsExplore key concepts in thermal physics, including internal energy, specific heat capacity, and the ideal gas law. This summary covers the relationships between temperature, pressure, and volume, as well as the kinetic theory of gases and latent heat. Ideal for A-Level physics students seeking a concise overview of essential topics.
PhysicsExplore the fundamental concepts of particle physics, including the structure of atoms, the classification of subatomic particles (hadrons, leptons, baryons, and mesons), and the significance of isotopes. This summary provides essential equations for calculating specific charge and examples of various particles, making it a valuable resource for A-Level physics students.
PhysicsApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Nikolay
@nikolay
Nuclear physics explores the fascinating world inside atoms, where tiny particles can pack enormous energy and some nuclei naturally break apart through radioactive decay. Understanding these concepts is crucial for grasping everything from medical treatments to energy production.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Nuclear physics starts with understanding what's actually inside an atom's nucleus. An alpha particle is essentially a helium nucleus containing 2 protons and 2 neutrons, which you'll see written as ₄²α in nuclear equations.
Rutherford's gold leaf experiment was the groundbreaking investigation that first revealed the nuclear structure of atoms. This experiment showed that atoms aren't just "plum puddings" of charge, but have dense, tiny nuclei at their centres.
Key Insight: The nucleus is incredibly small compared to the whole atom, yet contains nearly all the atom's mass.
This experiment laid the foundation for our modern understanding of atomic structure and nuclear physics.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
You can actually measure how big a nucleus is by firing high-energy electrons at it and watching the diffraction pattern that forms. When electrons hit the nucleus, they create circular patterns with dark spots called minima.
The key formula for nuclear radius is R = A₀A^(1/3), where A₀ ≈ 1.4 fm (femtometres) and A is the mass number. This tells us that bigger nuclei aren't just scaled-up versions of smaller ones.
Here's how the maths works: if you fire 300 MeV electrons and get your first minimum at 30°, you can calculate the wavelength using E = hf = hc/λ. Then use R = 1.22λ/(2sinθ) to find the nuclear radius.
Pro Tip: Remember that E = hf works for particles too, not just photons - this is crucial for electron diffraction calculations.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Some nuclei are naturally unstable and will spontaneously break apart to become more stable. Think of it like a wobbly chair that eventually tips over - it's inevitable, but you can't predict exactly when.
Nuclear instability happens for several reasons: too many or too few neutrons, or simply too much energy packed into the nucleus. When nuclei decay, they release particles or energy to reach a more stable state.
This process creates ionising radiation - radiation powerful enough to knock electrons off atoms and damage living tissue. The decay rate decreases over time, but each individual decay is completely random and spontaneous.
Remember: Radioactive decay is like popcorn popping - you know roughly how long the whole process takes, but you can't predict which kernel pops next.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
There are four main types of nuclear radiation, each with different properties and dangers. Alpha particles (α) are heavy helium nuclei with +2 charge - they're slow but highly ionising and easily stopped by paper or skin.
Beta particles come in two flavours: beta-minus (β⁻) are electrons, while beta-plus (β⁺) are positrons. Both are much faster than alpha particles and can penetrate several millimetres of aluminium.
Gamma rays (γ) are electromagnetic waves with no mass or charge. They travel at the speed of light and can penetrate deep into materials - you need thick lead or concrete to stop them.
Safety Alert: Alpha particles are most dangerous when ingested because they cause massive internal damage, while gamma rays can harm you from a distance.
The penetrating power increases dramatically: paper stops alpha, aluminium stops beta, but only dense materials like lead can stop gamma radiation effectively.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Protecting yourself from radiation exposure follows three simple principles: time, distance, and shielding. Spend less time near sources, stay further away, and put barriers between you and the radiation.
The inverse square law explains why distance is so effective: I = k/x². This means if you double your distance from a radiation source, the intensity drops to just one-quarter of its original value.
This law works perfectly for gamma rays and applies to alpha and beta particles too, but only in a vacuum. In air, alpha and beta particles lose energy through collisions, so they don't travel as far.
Real-world Application: This is why nuclear workers use long-handled tools and work behind thick shields - small increases in distance provide huge safety benefits.
Remember that gamma radiation spreads in all directions from its source, making the inverse square law particularly important for calculating safe working distances.
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
9
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the mechanisms of particle interactions through exchange particles and Feynman diagrams. This summary covers key concepts such as beta decay, fundamental forces, and the role of bosons in particle physics, essential for exam preparation.
PhysicsExplore detailed notes covering essential A-Level Physics concepts, including stellar luminosity, electromagnetic radiation, nuclear decay, and gas laws. This resource is designed for AQA and other exam boards, featuring interactive flashcard-style navigation for effective revision. Access the full notes here: https://www.notion.so/Physics-Revision-AQA-A-Level-a87264d9f28c4302b.
PhysicsComprehensive revision notes on Thermal Physics, including key concepts such as phase changes, specific latent heat, the ideal gas law, and the first law of thermodynamics. Ideal for AQA A Level Physics students preparing for exams, with practice questions included to enhance understanding.
PhysicsExplore essential Feynman Diagrams for AQA A Level Physics, covering proton-proton collisions, electron interactions, and beta decay processes. This summary provides a clear understanding of subatomic particle interactions and nuclear equations, crucial for mastering Unit 2: Particles and Radiation.
PhysicsExplore key concepts in thermal physics, including internal energy, specific heat capacity, and the ideal gas law. This summary covers the relationships between temperature, pressure, and volume, as well as the kinetic theory of gases and latent heat. Ideal for A-Level physics students seeking a concise overview of essential topics.
PhysicsExplore the fundamental concepts of particle physics, including the structure of atoms, the classification of subatomic particles (hadrons, leptons, baryons, and mesons), and the significance of isotopes. This summary provides essential equations for calculating specific charge and examples of various particles, making it a valuable resource for A-Level physics students.
PhysicsApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Sociology