Maths
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English Language
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Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
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1l the quest for political stability: germany, 1871-1991
Britain & the wider world: 1745 -1901
The cold war
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
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
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Britain: 1509 -1745
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Biology
28 Nov 2025
254
6 pages
Your eyes are incredible organs that let you see the world around you - from reading your phone... Show more
Think of your eye like a sophisticated camera that's constantly taking pictures and sending them to your brain. Just like a camera needs different parts working together to create a clear image, your eye has multiple components that must coordinate perfectly for you to see properly.
The eye is basically a biological machine designed to capture light and convert it into electrical signals your brain can understand. When this system works smoothly, you get crystal-clear vision of everything around you.
Quick Fact Your eye processes visual information faster than any camera ever made!
Your eye has nine key parts, each with a specific job in creating vision. The cornea acts like a clear window cover that bends light as it enters your eye. Right behind it, the coloured iris contains muscles that control your pupil - that small black hole where light actually gets in.
The lens is your eye's adjustable focus system, held in place by suspensory ligaments and controlled by ciliary muscles that change its shape. The tough white sclera protects everything inside, whilst the retina at the back contains special cells that detect light.
Finally, the optic nerve works like a high-speed data cable, carrying electrical signals from your retina straight to your brain for processing.
Remember Each part depends on the others - if one isn't working properly, your vision suffers!
Ever wondered why bright lights make you squint? That's your iris reflex protecting your retina from damage - it's like having built-in sunglasses that adjust automatically.
When light receptors in your retina detect bright light, they trigger an immediate response. The iris muscles contract whilst the radial muscles relax, making your pupil smaller to reduce the amount of light hitting your retina.
In darker conditions, the exact opposite happens - your pupil dilates (gets bigger) to let more light in so you can see better. This whole process is completely automatic, so you never have to think about it.
Cool Fact This reflex happens in milliseconds - faster than you can blink!
If you can see your phone clearly but struggle to read the whiteboard from the back of the classroom, you're probably short-sighted. This incredibly common condition affects loads of teenagers and is easily fixable.
Myopia happens when your eyeball is too long or your cornea is too curved. Instead of light focusing directly on your retina, it focuses just in front of it, creating blurry images of distant objects.
The good news? A concave lens (the type that curves inward) can correct this perfectly. These lenses spread the light out slightly before it enters your eye, ensuring it focuses exactly where it should on your retina.
Did You Know Short-sightedness is becoming more common, especially among students who spend lots of time looking at screens!
Long-sightedness is the opposite problem - you can see distant objects clearly but struggle with close-up tasks like reading or using your phone. It's less common in teenagers but still affects many people.
This condition occurs when your eyeball is too short, your lens is too weak, or your cornea isn't curved enough. Light would focus behind your retina rather than directly on it, making nearby objects appear blurry.
A convex lens (which curves outward) solves this by converging light rays before they enter your eye. This ensures the light focuses precisely on your retina, giving you sharp vision at all distances.
Handy Tip Many people develop long-sightedness as they age, which is why older adults often need reading glasses!
Beyond traditional glasses, you've got several modern options for correcting vision problems. Contact lenses sit directly on your eye and are brilliant for sports or when you don't want to wear glasses - though they do require careful hygiene to prevent infections.
Laser eye surgery uses precise laser beams to reshape your cornea, potentially eliminating your need for glasses completely. It's incredibly accurate but does carry small risks of complications that you'd need to discuss with a specialist.
Replacement lens surgery involves swapping your natural lens for an artificial one. This option typically has higher risks, including potential retina damage, so it's usually reserved for severe cases or when other treatments won't work.
Important Always consult an eye specialist before considering any surgical treatments - they'll help you understand what's best for your specific situation!
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.
2
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the structure and function of the human nervous system, including neurons, reflex arcs, and the adaptation of the eye. This summary covers key concepts such as neural transmission, synapses, and the anatomy of the eye, providing essential insights for AQA GCSE students.
BiologyExplore the intricate relationship between the nervous system and eye anatomy in this comprehensive study resource. Covering key concepts such as synaptic transmission, visual processes, and the structure of photoreceptors, this material is tailored for Edexcel IGCSE Biology students. Understand how the eye accommodates for vision and the role of sensory receptors in perception.
BiologyExplore the anatomy and function of the human eye in this GCSE AQA Biology summary. Key topics include the cornea, retina, fovea, cones and rods, and the mechanisms of accommodation. Understand conditions like myopia and hyperopia, and how the eye adapts to different light conditions through circular and radial muscles.
BiologyExplore the detailed structure and functions of the human eye, including the roles of the sclera, cornea, iris, and lens. Understand vision defects like myopia and hyperopia, and learn about corrective treatments such as contact lenses and laser surgery. This summary is essential for GCSE biology students focusing on eye anatomy and visual processes.
BiologyExplore the structure and function of the human eye, including myopia, hyperopia, and the role of the iris, lens, and retina in vision. This summary covers key concepts such as light refraction, accommodation, and the visual process, essential for GCSE biology students.
BiologyExplore the intricate structures of the eye and brain, including common defects like myopia and hyperopia, and their corrective treatments. This summary covers key concepts such as eye anatomy, brain structure, and neuroimaging techniques, providing a comprehensive overview for students studying human biology.
BiologyApp 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
Your eyes are incredible organs that let you see the world around you - from reading your phone to spotting your mates across the school playground. Understanding how they work and what can go wrong helps explain why some people... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of your eye like a sophisticated camera that's constantly taking pictures and sending them to your brain. Just like a camera needs different parts working together to create a clear image, your eye has multiple components that must coordinate perfectly for you to see properly.
The eye is basically a biological machine designed to capture light and convert it into electrical signals your brain can understand. When this system works smoothly, you get crystal-clear vision of everything around you.
Quick Fact: Your eye processes visual information faster than any camera ever made!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your eye has nine key parts, each with a specific job in creating vision. The cornea acts like a clear window cover that bends light as it enters your eye. Right behind it, the coloured iris contains muscles that control your pupil - that small black hole where light actually gets in.
The lens is your eye's adjustable focus system, held in place by suspensory ligaments and controlled by ciliary muscles that change its shape. The tough white sclera protects everything inside, whilst the retina at the back contains special cells that detect light.
Finally, the optic nerve works like a high-speed data cable, carrying electrical signals from your retina straight to your brain for processing.
Remember: Each part depends on the others - if one isn't working properly, your vision suffers!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered why bright lights make you squint? That's your iris reflex protecting your retina from damage - it's like having built-in sunglasses that adjust automatically.
When light receptors in your retina detect bright light, they trigger an immediate response. The iris muscles contract whilst the radial muscles relax, making your pupil smaller to reduce the amount of light hitting your retina.
In darker conditions, the exact opposite happens - your pupil dilates (gets bigger) to let more light in so you can see better. This whole process is completely automatic, so you never have to think about it.
Cool Fact: This reflex happens in milliseconds - faster than you can blink!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
If you can see your phone clearly but struggle to read the whiteboard from the back of the classroom, you're probably short-sighted. This incredibly common condition affects loads of teenagers and is easily fixable.
Myopia happens when your eyeball is too long or your cornea is too curved. Instead of light focusing directly on your retina, it focuses just in front of it, creating blurry images of distant objects.
The good news? A concave lens (the type that curves inward) can correct this perfectly. These lenses spread the light out slightly before it enters your eye, ensuring it focuses exactly where it should on your retina.
Did You Know: Short-sightedness is becoming more common, especially among students who spend lots of time looking at screens!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Long-sightedness is the opposite problem - you can see distant objects clearly but struggle with close-up tasks like reading or using your phone. It's less common in teenagers but still affects many people.
This condition occurs when your eyeball is too short, your lens is too weak, or your cornea isn't curved enough. Light would focus behind your retina rather than directly on it, making nearby objects appear blurry.
A convex lens (which curves outward) solves this by converging light rays before they enter your eye. This ensures the light focuses precisely on your retina, giving you sharp vision at all distances.
Handy Tip: Many people develop long-sightedness as they age, which is why older adults often need reading glasses!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Beyond traditional glasses, you've got several modern options for correcting vision problems. Contact lenses sit directly on your eye and are brilliant for sports or when you don't want to wear glasses - though they do require careful hygiene to prevent infections.
Laser eye surgery uses precise laser beams to reshape your cornea, potentially eliminating your need for glasses completely. It's incredibly accurate but does carry small risks of complications that you'd need to discuss with a specialist.
Replacement lens surgery involves swapping your natural lens for an artificial one. This option typically has higher risks, including potential retina damage, so it's usually reserved for severe cases or when other treatments won't work.
Important: Always consult an eye specialist before considering any surgical treatments - they'll help you understand what's best for your specific situation!
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.
2
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the structure and function of the human nervous system, including neurons, reflex arcs, and the adaptation of the eye. This summary covers key concepts such as neural transmission, synapses, and the anatomy of the eye, providing essential insights for AQA GCSE students.
BiologyExplore the intricate relationship between the nervous system and eye anatomy in this comprehensive study resource. Covering key concepts such as synaptic transmission, visual processes, and the structure of photoreceptors, this material is tailored for Edexcel IGCSE Biology students. Understand how the eye accommodates for vision and the role of sensory receptors in perception.
BiologyExplore the anatomy and function of the human eye in this GCSE AQA Biology summary. Key topics include the cornea, retina, fovea, cones and rods, and the mechanisms of accommodation. Understand conditions like myopia and hyperopia, and how the eye adapts to different light conditions through circular and radial muscles.
BiologyExplore the detailed structure and functions of the human eye, including the roles of the sclera, cornea, iris, and lens. Understand vision defects like myopia and hyperopia, and learn about corrective treatments such as contact lenses and laser surgery. This summary is essential for GCSE biology students focusing on eye anatomy and visual processes.
BiologyExplore the structure and function of the human eye, including myopia, hyperopia, and the role of the iris, lens, and retina in vision. This summary covers key concepts such as light refraction, accommodation, and the visual process, essential for GCSE biology students.
BiologyExplore the intricate structures of the eye and brain, including common defects like myopia and hyperopia, and their corrective treatments. This summary covers key concepts such as eye anatomy, brain structure, and neuroimaging techniques, providing a comprehensive overview for students studying human biology.
BiologyApp 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
