Maths
Chemistry
Biology
English Language
History
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
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
Show all topics
Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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
World war one
Britain: 1509 -1745
Show all topics
Physics
15 Dec 2025
151
8 pages
Grace <3 @harmonious123
Ever wondered how your mobile phone connects to the internet, or how doctors can see inside your body... Show more
Think of electromagnetic waves as invisible ripples of energy that zip through space at the speed of light - that's roughly 300 million metres per second! These waves are created when electric and magnetic fields vibrate, and they're transverse waves because the vibrations happen at right angles to the direction the wave travels.
The electromagnetic spectrum contains seven different types of waves, each with unique properties. From longest to shortest wavelength, they are radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. A handy way to remember this order is "Raging Mammals Invaded Venus Using X-ray Guns."
Here's the key pattern as wavelength gets shorter, frequency and energy increase. Radio waves have long wavelengths but low energy, whilst gamma rays have incredibly short wavelengths but massive amounts of energy.
Quick Tip The electromagnetic spectrum is like a sliding scale - each type of wave has its own special job based on its energy level!
Radio waves are the gentle giants of the electromagnetic spectrum, with wavelengths around 1 metre long. You encounter them constantly - every time you listen to music, watch TV, or play with a remote-controlled toy car, you're using radio wave technology.
These waves aren't just for entertainment though. Astronomers use radio waves to study distant stars and galaxies, measuring the radio signals these cosmic objects naturally produce to work out how far away they are.
Because radio waves have such low energy, they're completely safe for humans and can travel vast distances without losing much strength.
Did You Know? Radio waves from some TV programmes broadcast decades ago are still travelling through space right now!
Despite their name making you think of kitchen appliances, microwaves do much more than heat your leftover pizza! With wavelengths of about 1 centimetre, these waves are the backbone of modern communication - your WiFi, mobile phone, and GPS all rely on microwave technology.
Satellite communication uses microwaves to beam signals between Earth and space, which is how your satnav knows exactly where you are. However, microwaves can generate heat (as anyone who's used a microwave oven knows), so safety features like door locks prevent the waves from escaping.
The heating effect happens because microwaves make water molecules vibrate rapidly, creating friction and warmth - perfect for cooking, but potentially dangerous if not properly contained.
Safety First Microwave ovens won't operate with the door open because the waves could cause burns!
Every warm object around you - including your own body - constantly emits infrared radiation. With wavelengths of approximately 0.1mm, infrared is essentially heat energy you can't see but definitely feel.
You use infrared technology more than you realise TV remote controls, toasters, ovens, and even some internet connections rely on these waves. Thermal imaging cameras detect infrared to create heat maps, which is why night vision equipment can spot warm bodies in complete darkness.
While infrared is generally safe at normal levels, concentrated amounts can cause burns. This is why standing too close to a fire or hot oven can hurt your skin - you're absorbing too much infrared radiation.
Cool Fact Infrared cameras can detect heat leaks in buildings, helping save energy and reduce heating bills!
Visible light is the only electromagnetic radiation your eyes can detect, with wavelengths around 0.001mm. This narrow slice of the spectrum lets you see everything around you and makes life as we know it possible.
Beyond just vision, visible light has brilliant practical applications. Laser technology uses concentrated light beams for surgery, cutting materials, and sending internet signals through fibre optic cables. Cameras and video equipment capture and reproduce visible light to create images and films.
However, intense visible light can damage your eyes - looking directly at the sun or powerful lasers can cause permanent blindness. This is why welders wear special masks and you should never stare at bright lights.
Remember White light contains all colours of the rainbow - you can prove this by shining light through a glass prism!
Ultraviolet (UV) radiation has wavelengths of about 0.00001mm and packs enough energy to make certain materials glow. You've probably seen this effect with highlighter pens under UV lights - the special inks absorb UV and re-emit it as visible light.
Forensic scientists use UV radiation to detect forged documents like fake banknotes or passports, as genuine security features often only show up under UV light. Water treatment facilities also use UV to kill harmful bacteria and purify drinking water.
The sun produces intense UV radiation that can damage your skin cells' DNA, leading to sunburn and potentially skin cancer. This is why sunscreen and sunglasses are essential protection on sunny days.
Health Tip Even on cloudy days, UV rays can penetrate through and cause skin damage - daily sun protection is always wise!
X-rays have incredibly short wavelengths (around 10⁻¹⁰m) and enough energy to pass through soft tissues but get absorbed by dense materials like bones. This makes them perfect for medical imaging - doctors can see broken bones without invasive procedures.
Beyond hospitals, X-rays sterilise medical equipment by killing bacteria, and airport security scanners use them to peek inside luggage. Underground pipe detection and industrial quality control also rely on X-ray technology.
However, X-rays carry enough energy to damage DNA, which is why radiographers step behind protective screens during scans. Occasional medical X-rays pose minimal risk, but repeated exposure requires careful monitoring.
Medical Marvel A single chest X-ray exposes you to about the same amount of radiation you'd naturally receive in 10 days!
Gamma rays are the most energetic electromagnetic waves, with wavelengths of just 10⁻¹²m. Like X-rays, they're used in medical imaging and sterilising equipment, but their extreme energy makes them incredibly powerful tools.
Food industry uses gamma rays to kill bacteria in fresh produce, extending shelf life without chemicals. In medicine, gamma radiation can both detect and treat cancer - it's precise enough to target tumour cells whilst minimising damage to healthy tissue.
The high energy that makes gamma rays useful also makes them dangerous. They can severely damage DNA and cause cancer, so people working with radioactive materials must wear protective clothing and limit exposure time.
Amazing Application Gamma rays from space help astronomers study black holes and other extreme cosmic events!
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.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Quotes from every main character
English LiteratureApp 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
Grace <3
@harmonious123
Ever wondered how your mobile phone connects to the internet, or how doctors can see inside your body without cutting you open? The answer lies in electromagnetic waves - invisible energy waves that surround us every day and power most... 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 electromagnetic waves as invisible ripples of energy that zip through space at the speed of light - that's roughly 300 million metres per second! These waves are created when electric and magnetic fields vibrate, and they're transverse waves because the vibrations happen at right angles to the direction the wave travels.
The electromagnetic spectrum contains seven different types of waves, each with unique properties. From longest to shortest wavelength, they are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. A handy way to remember this order is "Raging Mammals Invaded Venus Using X-ray Guns."
Here's the key pattern: as wavelength gets shorter, frequency and energy increase. Radio waves have long wavelengths but low energy, whilst gamma rays have incredibly short wavelengths but massive amounts of energy.
Quick Tip: The electromagnetic spectrum is like a sliding scale - each type of wave has its own special job based on its energy level!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Radio waves are the gentle giants of the electromagnetic spectrum, with wavelengths around 1 metre long. You encounter them constantly - every time you listen to music, watch TV, or play with a remote-controlled toy car, you're using radio wave technology.
These waves aren't just for entertainment though. Astronomers use radio waves to study distant stars and galaxies, measuring the radio signals these cosmic objects naturally produce to work out how far away they are.
Because radio waves have such low energy, they're completely safe for humans and can travel vast distances without losing much strength.
Did You Know? Radio waves from some TV programmes broadcast decades ago are still travelling through space right now!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Despite their name making you think of kitchen appliances, microwaves do much more than heat your leftover pizza! With wavelengths of about 1 centimetre, these waves are the backbone of modern communication - your WiFi, mobile phone, and GPS all rely on microwave technology.
Satellite communication uses microwaves to beam signals between Earth and space, which is how your satnav knows exactly where you are. However, microwaves can generate heat (as anyone who's used a microwave oven knows), so safety features like door locks prevent the waves from escaping.
The heating effect happens because microwaves make water molecules vibrate rapidly, creating friction and warmth - perfect for cooking, but potentially dangerous if not properly contained.
Safety First: Microwave ovens won't operate with the door open because the waves could cause burns!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Every warm object around you - including your own body - constantly emits infrared radiation. With wavelengths of approximately 0.1mm, infrared is essentially heat energy you can't see but definitely feel.
You use infrared technology more than you realise: TV remote controls, toasters, ovens, and even some internet connections rely on these waves. Thermal imaging cameras detect infrared to create heat maps, which is why night vision equipment can spot warm bodies in complete darkness.
While infrared is generally safe at normal levels, concentrated amounts can cause burns. This is why standing too close to a fire or hot oven can hurt your skin - you're absorbing too much infrared radiation.
Cool Fact: Infrared cameras can detect heat leaks in buildings, helping save energy and reduce heating bills!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Visible light is the only electromagnetic radiation your eyes can detect, with wavelengths around 0.001mm. This narrow slice of the spectrum lets you see everything around you and makes life as we know it possible.
Beyond just vision, visible light has brilliant practical applications. Laser technology uses concentrated light beams for surgery, cutting materials, and sending internet signals through fibre optic cables. Cameras and video equipment capture and reproduce visible light to create images and films.
However, intense visible light can damage your eyes - looking directly at the sun or powerful lasers can cause permanent blindness. This is why welders wear special masks and you should never stare at bright lights.
Remember: White light contains all colours of the rainbow - you can prove this by shining light through a glass prism!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ultraviolet (UV) radiation has wavelengths of about 0.00001mm and packs enough energy to make certain materials glow. You've probably seen this effect with highlighter pens under UV lights - the special inks absorb UV and re-emit it as visible light.
Forensic scientists use UV radiation to detect forged documents like fake banknotes or passports, as genuine security features often only show up under UV light. Water treatment facilities also use UV to kill harmful bacteria and purify drinking water.
The sun produces intense UV radiation that can damage your skin cells' DNA, leading to sunburn and potentially skin cancer. This is why sunscreen and sunglasses are essential protection on sunny days.
Health Tip: Even on cloudy days, UV rays can penetrate through and cause skin damage - daily sun protection is always wise!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
X-rays have incredibly short wavelengths (around 10⁻¹⁰m) and enough energy to pass through soft tissues but get absorbed by dense materials like bones. This makes them perfect for medical imaging - doctors can see broken bones without invasive procedures.
Beyond hospitals, X-rays sterilise medical equipment by killing bacteria, and airport security scanners use them to peek inside luggage. Underground pipe detection and industrial quality control also rely on X-ray technology.
However, X-rays carry enough energy to damage DNA, which is why radiographers step behind protective screens during scans. Occasional medical X-rays pose minimal risk, but repeated exposure requires careful monitoring.
Medical Marvel: A single chest X-ray exposes you to about the same amount of radiation you'd naturally receive in 10 days!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Gamma rays are the most energetic electromagnetic waves, with wavelengths of just 10⁻¹²m. Like X-rays, they're used in medical imaging and sterilising equipment, but their extreme energy makes them incredibly powerful tools.
Food industry uses gamma rays to kill bacteria in fresh produce, extending shelf life without chemicals. In medicine, gamma radiation can both detect and treat cancer - it's precise enough to target tumour cells whilst minimising damage to healthy tissue.
The high energy that makes gamma rays useful also makes them dangerous. They can severely damage DNA and cause cancer, so people working with radioactive materials must wear protective clothing and limit exposure time.
Amazing Application: Gamma rays from space help astronomers study black holes and other extreme cosmic events!
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.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Quotes from every main character
English LiteratureApp 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