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25 Dec 2025
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Understanding P13 Electromagnetic Waves: Key Concepts Explained
J
J
@j.isanerd
1 / 6
The Electromagnetic Spectrum
Ever wondered what connects your mobile phone to radio stations and hospital X-ray machines? They all use different parts of the electromagnetic spectrum, which is basically a family of waves arranged by their properties.
The spectrum runs from radio waves (longest wavelength, lowest energy) through microwaves, infrared, visible light, ultraviolet, X-rays, to gamma rays (shortest wavelength, highest energy). Your eyes can only detect visible light, which has wavelengths between about 350-650 nanometres.
All electromagnetic waves transfer energy from one place to another using the wave equation v = f × λ . White light contains all colours of the visible spectrum mixed together.
Quick Tip: Remember the spectrum order with "Really Mad Insects Visit Using eXtreme Games" - Radio, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma!
Light, Infrared, Microwaves and Radio Waves
These waves are the workhorses of modern communication and they're generally safe for everyday use. Infrared radiation powers your TV remote and carries signals through optical fibres at lightning speed.
Microwaves are brilliant for satellite TV and mobile phone calls because they can travel long distances and carry lots of information. Your mobile actually uses microwave radiation mixed with radio waves at similar frequencies.
However, these waves aren't completely harmless. Microwaves and radio waves can heat up the inside of your body (think microwave oven!), whilst infrared can cause nasty skin burns if you're exposed to too much.
Did You Know? The same microwaves that heat your food also carry your Netflix shows from satellites in space!
Required Practical: Infrared Absorption and Emission
This experiment shows you which surfaces are best at absorbing and giving off infrared radiation - crucial knowledge for understanding heat transfer and energy efficiency.
Take two identical cans - one shiny and light, one matt and black. Fill both with hot water at the same temperature, wait 20 minutes, then measure temperatures. The cooler can has the surface that's the best emitter of infrared.
Now fill both cans with cold water and place them in sunlight for 30 minutes. The warmer can has the surface that's the best absorber of infrared. You'll find that dark, matt surfaces both absorb and emit infrared better than light, shiny ones.
Real-World Connection: This is why radiators are often painted with matt paint and why wearing black clothes makes you hotter in summer!
Communications Technology
Different radio wave frequencies behave differently - some travel further, others carry more information, and some spread out more than others. This is why radio stations, satellite TV, and mobile networks all use specific frequency ranges.
Microwaves are perfect for satellite TV because they can punch through the atmosphere without getting scattered. Optical fibres are incredibly thin, transparent cables that use light and infrared to carry communication signals at massive speeds.
The system works using carrier waves - these are base waves that carry information by changing their amplitude (strength). Scientists are still researching whether mobile phone radiation is completely safe for long-term use.
Tech Fact: Optical fibres can carry thousands of phone calls simultaneously and are almost impossible to tap into - perfect for secure communications!
Ultraviolet, X-rays and Gamma Rays
Now we're entering the dangerous zone of the electromagnetic spectrum. Ultraviolet waves have shorter wavelengths than visible light and can seriously damage your skin and eyes - think sunburn and cataracts.
X-rays are brilliant for medical imaging because they pass through soft tissue but get absorbed by bones and teeth. Gamma rays are the ultimate sterilisers - they kill bacteria in food, sterilise surgical equipment, and destroy cancer cells.
Both X-rays and gamma rays are ionising radiation, meaning they can knock electrons off atoms and damage living tissue. This makes them useful for medicine but potentially very dangerous.
Safety Note: This is why radiographers leave the room when taking X-rays - even small doses add up over time!
X-rays in Medicine
X-rays are incredibly useful in hospitals for two main jobs: creating images of your internal body parts and destroying tumours near the body surface. They work because bones absorb X-rays much more than soft tissues do.
Since X-rays are ionising radiation, hospital workers wear film badges that detect radiation exposure. These badges change colour when exposed to X-rays, helping keep staff safe from dangerous doses.
Sometimes doctors use contrast medium (a special dye) to make soft tissues like your stomach show up on X-ray images. This liquid absorbs X-rays better than normal tissue, creating clearer pictures for diagnosis.
Career Connection: Medical imaging is a growing field - radiographers, medical physicists, and technologists all work with this technology every day!
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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
Understanding P13 Electromagnetic Waves: Key Concepts Explained
J
J
@j.isanerd
The electromagnetic spectrum is everywhere around you - from the radio waves carrying your favourite songs to the X-rays used in hospitals. Understanding these different types of waves and their properties will help you grasp how modern technology works and... Show more
The Electromagnetic Spectrum
Ever wondered what connects your mobile phone to radio stations and hospital X-ray machines? They all use different parts of the electromagnetic spectrum, which is basically a family of waves arranged by their properties.
The spectrum runs from radio waves (longest wavelength, lowest energy) through microwaves, infrared, visible light, ultraviolet, X-rays, to gamma rays (shortest wavelength, highest energy). Your eyes can only detect visible light, which has wavelengths between about 350-650 nanometres.
All electromagnetic waves transfer energy from one place to another using the wave equation v = f × λ . White light contains all colours of the visible spectrum mixed together.
Quick Tip: Remember the spectrum order with "Really Mad Insects Visit Using eXtreme Games" - Radio, Microwaves, Infrared, Visible, Ultraviolet, X-rays, Gamma!
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
Light, Infrared, Microwaves and Radio Waves
These waves are the workhorses of modern communication and they're generally safe for everyday use. Infrared radiation powers your TV remote and carries signals through optical fibres at lightning speed.
Microwaves are brilliant for satellite TV and mobile phone calls because they can travel long distances and carry lots of information. Your mobile actually uses microwave radiation mixed with radio waves at similar frequencies.
However, these waves aren't completely harmless. Microwaves and radio waves can heat up the inside of your body (think microwave oven!), whilst infrared can cause nasty skin burns if you're exposed to too much.
Did You Know? The same microwaves that heat your food also carry your Netflix shows from satellites in space!
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
Required Practical: Infrared Absorption and Emission
This experiment shows you which surfaces are best at absorbing and giving off infrared radiation - crucial knowledge for understanding heat transfer and energy efficiency.
Take two identical cans - one shiny and light, one matt and black. Fill both with hot water at the same temperature, wait 20 minutes, then measure temperatures. The cooler can has the surface that's the best emitter of infrared.
Now fill both cans with cold water and place them in sunlight for 30 minutes. The warmer can has the surface that's the best absorber of infrared. You'll find that dark, matt surfaces both absorb and emit infrared better than light, shiny ones.
Real-World Connection: This is why radiators are often painted with matt paint and why wearing black clothes makes you hotter in summer!
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
Communications Technology
Different radio wave frequencies behave differently - some travel further, others carry more information, and some spread out more than others. This is why radio stations, satellite TV, and mobile networks all use specific frequency ranges.
Microwaves are perfect for satellite TV because they can punch through the atmosphere without getting scattered. Optical fibres are incredibly thin, transparent cables that use light and infrared to carry communication signals at massive speeds.
The system works using carrier waves - these are base waves that carry information by changing their amplitude (strength). Scientists are still researching whether mobile phone radiation is completely safe for long-term use.
Tech Fact: Optical fibres can carry thousands of phone calls simultaneously and are almost impossible to tap into - perfect for secure communications!
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
Ultraviolet, X-rays and Gamma Rays
Now we're entering the dangerous zone of the electromagnetic spectrum. Ultraviolet waves have shorter wavelengths than visible light and can seriously damage your skin and eyes - think sunburn and cataracts.
X-rays are brilliant for medical imaging because they pass through soft tissue but get absorbed by bones and teeth. Gamma rays are the ultimate sterilisers - they kill bacteria in food, sterilise surgical equipment, and destroy cancer cells.
Both X-rays and gamma rays are ionising radiation, meaning they can knock electrons off atoms and damage living tissue. This makes them useful for medicine but potentially very dangerous.
Safety Note: This is why radiographers leave the room when taking X-rays - even small doses add up over time!
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
X-rays in Medicine
X-rays are incredibly useful in hospitals for two main jobs: creating images of your internal body parts and destroying tumours near the body surface. They work because bones absorb X-rays much more than soft tissues do.
Since X-rays are ionising radiation, hospital workers wear film badges that detect radiation exposure. These badges change colour when exposed to X-rays, helping keep staff safe from dangerous doses.
Sometimes doctors use contrast medium (a special dye) to make soft tissues like your stomach show up on X-ray images. This liquid absorbs X-rays better than normal tissue, creating clearer pictures for diagnosis.
Career Connection: Medical imaging is a growing field - radiographers, medical physicists, and technologists all work with this technology every day!
We thought you’d 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?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
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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Students love us — and so will you.
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 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