Biology
Chemistry
AP Chemistry
English
AP English Literature
Physics
Dec 8, 2025
101
2 pages
Los @los
Ever wondered why dark clothes feel hotter in the sun or how doctors safely use X-rays? This covers... Show more
Here's something that might surprise you - the amount of infrared radiation an object gives off doesn't just depend on how hot it is. The surface material makes a massive difference too, which is why your black t-shirt feels scorching on a sunny day whilst a white one stays cooler.
Scientists use a clever device called a Leslie cube to investigate this. It's basically a metal cube filled with hot water, but each side has a different surface - matt black paint, matt white paint, shiny metal, and dull metal. Since it's the same cube filled with the same hot water, all sides are exactly the same temperature.
When you measure the infrared radiation coming from each face using an infrared detector, you'll find that darker surfaces emit much more IR than lighter ones. Matt surfaces also give off more radiation than shiny ones - that's why radiators are often painted with matt paint rather than being left shiny.
Quick Tip Remember "BADS" - Black surfaces Absorb more, Dark surfaces emit more, Shiny surfaces reflect more!
The same principle works for absorption. In a classic experiment, identical metal plates with different coloured surfaces (one matt black, one silver) are placed near a flame. Each has a ball bearing stuck on with wax. The ball bearing on the black plate always falls first because black surfaces absorb infrared radiation much more effectively, melting the wax faster.
Not all electromagnetic radiation is created equal when it comes to your health. The key factor is energy - and higher frequency waves pack a much more dangerous punch than their low-frequency cousins.
Radio waves and other low-frequency radiation are pretty harmless. They don't carry enough energy to damage your cells and mostly just pass straight through your body. But as you move up the electromagnetic spectrum, things get more serious.
UV radiation from the sun damages surface cells, causing sunburn and premature skin ageing. More worryingly, it can damage your eyes (potentially causing blindness) and significantly increase your risk of skin cancer. That's why factor 30 sunscreen and sunglasses aren't just fashion accessories.
X-rays and gamma rays are the real heavy hitters. These are types of ionising radiation, meaning they carry enough energy to knock electrons clean off atoms. This can kill cells outright or cause gene mutations that lead to cancer.
Remember The higher the frequency, the more energy the wave carries, and the more damage it can potentially cause.
Despite the risks, these dangerous radiations are incredibly useful in medicine. We measure exposure using radiation dose in sieverts (Sv), which considers not just how much radiation you've absorbed, but also which body tissues were affected and what type of radiation it was. This helps doctors balance the benefits of medical imaging and treatment against the potential risks.
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the 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
Explore the fundamentals of electromagnetic waves, including the electromagnetic spectrum, wave properties, and applications in technology and medicine. This comprehensive guide covers key concepts such as refraction, radiation types, and the behavior of light and sound. Ideal for students preparing for exams in physics, this resource includes diagrams, calculations, and practical examples to enhance understanding.
PhysicsGood
PhysicsThis involves concepts in electromagnetic spectrum and its classifications.
PhysicsExplore the definitions, sources, and safety measures related to background radiation, contamination, and irradiation. Understand the risks of cell damage, mutations, and cancer associated with radiation exposure. This summary provides essential insights for students studying radiation effects and safety protocols.
PhysicsExplore the visible light spectrum, including the properties of colors, how objects appear based on light interaction, and the function of color filters. This summary covers key concepts such as opaque, transparent, and translucent materials, and the science behind color perception. Ideal for students studying light phenomena.
PhysicsWAVES (paper 2 AQA)
PhysicsApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Los
@los
Ever wondered why dark clothes feel hotter in the sun or how doctors safely use X-rays? This covers two fascinating areas of physics: investigating how different surfaces emit and absorb infrared radiation, and understanding the potential dangers of electromagnetic radiation... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's something that might surprise you - the amount of infrared radiation an object gives off doesn't just depend on how hot it is. The surface material makes a massive difference too, which is why your black t-shirt feels scorching on a sunny day whilst a white one stays cooler.
Scientists use a clever device called a Leslie cube to investigate this. It's basically a metal cube filled with hot water, but each side has a different surface - matt black paint, matt white paint, shiny metal, and dull metal. Since it's the same cube filled with the same hot water, all sides are exactly the same temperature.
When you measure the infrared radiation coming from each face using an infrared detector, you'll find that darker surfaces emit much more IR than lighter ones. Matt surfaces also give off more radiation than shiny ones - that's why radiators are often painted with matt paint rather than being left shiny.
Quick Tip: Remember "BADS" - Black surfaces Absorb more, Dark surfaces emit more, Shiny surfaces reflect more!
The same principle works for absorption. In a classic experiment, identical metal plates with different coloured surfaces (one matt black, one silver) are placed near a flame. Each has a ball bearing stuck on with wax. The ball bearing on the black plate always falls first because black surfaces absorb infrared radiation much more effectively, melting the wax faster.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Not all electromagnetic radiation is created equal when it comes to your health. The key factor is energy - and higher frequency waves pack a much more dangerous punch than their low-frequency cousins.
Radio waves and other low-frequency radiation are pretty harmless. They don't carry enough energy to damage your cells and mostly just pass straight through your body. But as you move up the electromagnetic spectrum, things get more serious.
UV radiation from the sun damages surface cells, causing sunburn and premature skin ageing. More worryingly, it can damage your eyes (potentially causing blindness) and significantly increase your risk of skin cancer. That's why factor 30 sunscreen and sunglasses aren't just fashion accessories.
X-rays and gamma rays are the real heavy hitters. These are types of ionising radiation, meaning they carry enough energy to knock electrons clean off atoms. This can kill cells outright or cause gene mutations that lead to cancer.
Remember: The higher the frequency, the more energy the wave carries, and the more damage it can potentially cause.
Despite the risks, these dangerous radiations are incredibly useful in medicine. We measure exposure using radiation dose in sieverts (Sv), which considers not just how much radiation you've absorbed, but also which body tissues were affected and what type of radiation it was. This helps doctors balance the benefits of medical imaging and treatment against the potential risks.
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the 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
Explore the fundamentals of electromagnetic waves, including the electromagnetic spectrum, wave properties, and applications in technology and medicine. This comprehensive guide covers key concepts such as refraction, radiation types, and the behavior of light and sound. Ideal for students preparing for exams in physics, this resource includes diagrams, calculations, and practical examples to enhance understanding.
PhysicsGood
PhysicsThis involves concepts in electromagnetic spectrum and its classifications.
PhysicsExplore the definitions, sources, and safety measures related to background radiation, contamination, and irradiation. Understand the risks of cell damage, mutations, and cancer associated with radiation exposure. This summary provides essential insights for students studying radiation effects and safety protocols.
PhysicsExplore the visible light spectrum, including the properties of colors, how objects appear based on light interaction, and the function of color filters. This summary covers key concepts such as opaque, transparent, and translucent materials, and the science behind color perception. Ideal for students studying light phenomena.
PhysicsWAVES (paper 2 AQA)
PhysicsApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
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