Light is everywhere around us, and understanding how it behaves... Show more
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Maya ๐ค
18/12/2025
Physics
S2 Light Topic Summary Notes
230
โข
18 Dec 2025
โข
S2 Light Study Guide & Topic Notes
Maya ๐ค
@foxkrolowa
1 / 7
Light Basics and Reflection
Ever wondered why lightning appears before you hear thunder? It's because light waves travel much faster than sound waves! Light always travels in straight lines called light rays, which is why shadows form when light gets blocked.
The sun and light bulbs are light sources because they actually emit light, whilst the moon just reflects sunlight back to us. What we see as white light is actually made up of seven different colours - the visible spectrum that creates rainbows.
When light hits a mirror, it follows the Law of Reflection: the angle of incidence always equals the angle of reflection. Picture a ball bouncing off a wall at exactly the same angle it hits - that's how light behaves too.
Top Tip: Always use a ruler when drawing light diagrams, and remember that angles are measured from the normal line (the perpendicular line to the surface), not from the mirror itself!
Curved Mirrors and Total Internal Reflection
Concave mirrors curve inward like a cave and bring light rays together to a focus point - think of them as "collecting" light. Convex mirrors bulge outward and spread light rays apart, which is why shop security mirrors give you that wide "fish-eye" view.
Total internal reflection is a clever trick that happens when light hits the inside surface of a material at just the right angle. Instead of passing through, it bounces back completely, turning the surface into a perfect mirror.
This amazing property makes optical fibres possible. These thin glass cables use total internal reflection to carry light (and data) over long distances without losing it.
Real-World Connection: Doctors use optical fibres in endoscopes to see inside your body without surgery - the light bounces along the curved cable to illuminate hard-to-reach places!
Refraction - When Light Bends
Refraction happens when light changes speed as it moves between different materials, causing it to change direction. It's like when you're walking from grass onto concrete - you might change pace and direction slightly.
When light enters glass from air, it bends towards the normal line. When it exits back into air, it bends away from the normal line. Remember "TAG-AGA": Towards Air to Glass, Away Glass to Air.
Here's the cool bit - when light exits a rectangular glass block, it emerges parallel to how it entered, just slightly shifted sideways. The angle of incidence and angle of refraction have a predictable relationship that changes depending on the materials involved.
Memory Helper: Think of light as a car driving from a road into mud - it slows down and changes direction, but when it gets back on the road, it speeds up and straightens out again!
Convex Lenses and the Human Eye
Convex lenses are like curved pieces of glass that bend light rays to meet at a focal point. They're basically doing the same job as your eye's lens! When objects are close to a convex lens, the image appears magnified and right-way up - that's how magnifying glasses work.
Move the object further away, and something interesting happens: the image becomes smaller and inverted . This is exactly what's happening in your eye right now as you read this.
The human eye has several key parts working together. The cornea is the tough, clear front layer that starts focusing light. The iris (the coloured bit) controls how much light enters through the pupil. The lens fine-tunes the focus onto the retina, where the image gets converted into electrical signals.
Amazing Fact: The image on your retina is actually upside-down! Your optic nerve sends this inverted image to your brain, which cleverly flips it the right way up for you.
Eye Structure and Function
Your eye is basically a sophisticated biological camera. Each part has a specific job that makes vision possible. The cornea acts like a window, letting light in while starting to focus it. The iris works like a camera's aperture, adjusting the pupil size to control light levels.
The lens is the fine-tuning mechanism - it's convex-shaped and focuses light rays precisely onto the retina. Think of the retina as your eye's film or digital sensor - it's packed with light-sensitive cells that capture the image.
The optic nerve is your biological data cable, carrying electrical signals from the retina straight to your brain. Your brain does the heavy lifting, processing these signals and correcting that upside-down image.
Quick Check: Try covering one eye and looking around - notice how your iris adjusts the pupil size when moving between bright and dark areas. That's your eye automatically controlling its light exposure!
White Light and the Visible Spectrum
When white light passes through a triangular prism, something magical happens - it splits into all the colours of the rainbow! This process is called dispersion, and it proves that white light isn't actually white at all.
The visible spectrum contains seven colours in a specific order: Red, Orange, Yellow, Green, Blue, Indigo, Violet. You can remember this with "Richard Of York Gave Battle In Vain" or simply "ROY G. BIV".
This same dispersion happens naturally when sunlight passes through raindrops in the air, creating the rainbows we see after storms. Each colour bends slightly differently as it passes through the prism, which is why they separate out.
Nature Connection: Next time you see a rainbow, remember you're witnessing millions of tiny water droplets acting like mini-prisms, splitting sunlight into its component colours across the sky!
The Electromagnetic Spectrum
The electromagnetic spectrum is like a massive family of waves emitted by the Sun, and visible light is just one small part of it! There are seven main types, each with different properties and uses.
From most dangerous to least harmful, they are: Gamma rays (used to kill cancer cells), X-rays (for seeing bones), Ultraviolet (in fluorescent lights), Visible light (what we see), Infrared (remote controls and thermal imaging), Microwaves (cooking and radar), and Radio waves (broadcasting).
Remember the order with "Getting X-rayed Unveils Various Illnesses Making Treatment Rapid". Ultraviolet radiation from the Sun can cause skin cancer, which is why sun cream is so important - it blocks harmful UV rays.
Safety Note: Even though we can't see UV rays, they're still there on cloudy days! Always wear sun cream when spending time outdoors, especially during summer months.
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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.
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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
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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!
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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.
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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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
Xander S
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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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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
S2 Light Study Guide & Topic Notes
Maya ๐ค
@foxkrolowa
Light is everywhere around us, and understanding how it behaves is crucial for explaining everything from why we see rainbows to how our eyes work. This topic covers the fundamental properties of light, including how it travels, reflects, and bends... Show more
Light Basics and Reflection
Ever wondered why lightning appears before you hear thunder? It's because light waves travel much faster than sound waves! Light always travels in straight lines called light rays, which is why shadows form when light gets blocked.
The sun and light bulbs are light sources because they actually emit light, whilst the moon just reflects sunlight back to us. What we see as white light is actually made up of seven different colours - the visible spectrum that creates rainbows.
When light hits a mirror, it follows the Law of Reflection: the angle of incidence always equals the angle of reflection. Picture a ball bouncing off a wall at exactly the same angle it hits - that's how light behaves too.
Top Tip: Always use a ruler when drawing light diagrams, and remember that angles are measured from the normal line (the perpendicular line to the surface), not from the mirror itself!
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Curved Mirrors and Total Internal Reflection
Concave mirrors curve inward like a cave and bring light rays together to a focus point - think of them as "collecting" light. Convex mirrors bulge outward and spread light rays apart, which is why shop security mirrors give you that wide "fish-eye" view.
Total internal reflection is a clever trick that happens when light hits the inside surface of a material at just the right angle. Instead of passing through, it bounces back completely, turning the surface into a perfect mirror.
This amazing property makes optical fibres possible. These thin glass cables use total internal reflection to carry light (and data) over long distances without losing it.
Real-World Connection: Doctors use optical fibres in endoscopes to see inside your body without surgery - the light bounces along the curved cable to illuminate hard-to-reach places!
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Refraction - When Light Bends
Refraction happens when light changes speed as it moves between different materials, causing it to change direction. It's like when you're walking from grass onto concrete - you might change pace and direction slightly.
When light enters glass from air, it bends towards the normal line. When it exits back into air, it bends away from the normal line. Remember "TAG-AGA": Towards Air to Glass, Away Glass to Air.
Here's the cool bit - when light exits a rectangular glass block, it emerges parallel to how it entered, just slightly shifted sideways. The angle of incidence and angle of refraction have a predictable relationship that changes depending on the materials involved.
Memory Helper: Think of light as a car driving from a road into mud - it slows down and changes direction, but when it gets back on the road, it speeds up and straightens out again!
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Improve your grades
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Convex Lenses and the Human Eye
Convex lenses are like curved pieces of glass that bend light rays to meet at a focal point. They're basically doing the same job as your eye's lens! When objects are close to a convex lens, the image appears magnified and right-way up - that's how magnifying glasses work.
Move the object further away, and something interesting happens: the image becomes smaller and inverted . This is exactly what's happening in your eye right now as you read this.
The human eye has several key parts working together. The cornea is the tough, clear front layer that starts focusing light. The iris (the coloured bit) controls how much light enters through the pupil. The lens fine-tunes the focus onto the retina, where the image gets converted into electrical signals.
Amazing Fact: The image on your retina is actually upside-down! Your optic nerve sends this inverted image to your brain, which cleverly flips it the right way up for you.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
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By signing up you accept Terms of Service and Privacy Policy
Eye Structure and Function
Your eye is basically a sophisticated biological camera. Each part has a specific job that makes vision possible. The cornea acts like a window, letting light in while starting to focus it. The iris works like a camera's aperture, adjusting the pupil size to control light levels.
The lens is the fine-tuning mechanism - it's convex-shaped and focuses light rays precisely onto the retina. Think of the retina as your eye's film or digital sensor - it's packed with light-sensitive cells that capture the image.
The optic nerve is your biological data cable, carrying electrical signals from the retina straight to your brain. Your brain does the heavy lifting, processing these signals and correcting that upside-down image.
Quick Check: Try covering one eye and looking around - notice how your iris adjusts the pupil size when moving between bright and dark areas. That's your eye automatically controlling its light exposure!
Sign up to see the contentIt's free!
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Improve your grades
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White Light and the Visible Spectrum
When white light passes through a triangular prism, something magical happens - it splits into all the colours of the rainbow! This process is called dispersion, and it proves that white light isn't actually white at all.
The visible spectrum contains seven colours in a specific order: Red, Orange, Yellow, Green, Blue, Indigo, Violet. You can remember this with "Richard Of York Gave Battle In Vain" or simply "ROY G. BIV".
This same dispersion happens naturally when sunlight passes through raindrops in the air, creating the rainbows we see after storms. Each colour bends slightly differently as it passes through the prism, which is why they separate out.
Nature Connection: Next time you see a rainbow, remember you're witnessing millions of tiny water droplets acting like mini-prisms, splitting sunlight into its component colours across the sky!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Electromagnetic Spectrum
The electromagnetic spectrum is like a massive family of waves emitted by the Sun, and visible light is just one small part of it! There are seven main types, each with different properties and uses.
From most dangerous to least harmful, they are: Gamma rays (used to kill cancer cells), X-rays (for seeing bones), Ultraviolet (in fluorescent lights), Visible light (what we see), Infrared (remote controls and thermal imaging), Microwaves (cooking and radar), and Radio waves (broadcasting).
Remember the order with "Getting X-rayed Unveils Various Illnesses Making Treatment Rapid". Ultraviolet radiation from the Sun can cause skin cancer, which is why sun cream is so important - it blocks harmful UV rays.
Safety Note: Even though we can't see UV rays, they're still there on cloudy days! Always wear sun cream when spending time outdoors, especially during summer months.
We thought youโd never ask...
What is the Knowunity AI companion?
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.
Where can I download the Knowunity app?
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Is Knowunity really free of charge?
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4.9/5
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4.8/5
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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