Ever wondered how your phone connects to WiFi, how X-rays...
Physics57 views·Updated Jun 16, 2026·5 pagesUnderstanding Electromagnetic Waves
S
Savio Siby@avioiby_4nm7u9tda5z6
1 / 5
1
of 5
Electromagnetic Waves: Production and Dangers
Electromagnetic waves are created when atoms or their nuclei change energy states. Think of gamma rays shooting out from radioactive atoms, or radio waves being generated by the electrical circuits in your phone when you stream music.
Radio waves work through oscillations in electrical circuits - basically electricity wiggling back and forth really fast. Your TV aerial picks up these waves and converts them back into electrical signals with the same frequency. It's like a wireless electrical connection!
Some EM waves are properly dangerous though. Ultraviolet waves, X-rays and gamma rays can seriously damage your body tissues. We measure this danger using radiation dose in sieverts (Sv) - basically how much risk you're exposed to.
UV rays are sneaky - they make your skin age faster and increase skin cancer risk. X-rays and gamma rays are even worse because they're ionising radiation. This means they can knock electrons off atoms, messing up your DNA and potentially causing cancer. That's why radiographers hide behind lead screens during X-rays!
Key Point: The higher the radiation dose in sieverts, the greater the risk to your health - but don't panic, everyday exposure levels are incredibly low.
2
of 5
EM Wave Applications and Properties
Radio waves power your Bluetooth headphones, TV broadcasts, and can even bounce off the atmosphere to reach places directly blocked by mountains. Microwaves don't just heat your dinner - they also carry WiFi signals and communicate with satellites because they pass straight through the atmosphere.
In microwave ovens, the waves make water molecules vibrate rapidly, heating your food from the inside out. Infrared radiation is basically heat energy - thermal cameras detect it to see in the dark, and all objects emit it (hotter things emit more).
Visible light travels through fibre optic cables as pulses, carrying your broadband internet at light speed. The light bounces along the cable's length like a game of ping-pong. X-rays can pass through soft tissue but not bone, making them perfect for seeing fractures.
All EM waves can be reflected, refracted, absorbed or transmitted depending on what they hit. Understanding these properties helps explain why your WiFi struggles through thick walls but radio waves travel for miles.
Remember: Different EM waves interact with materials differently - that's why we use specific types for specific jobs.
3
of 5
Light, Colour and Infrared Radiation
The tiny slice of EM spectrum you can actually see gets split into different colours - each colour is just light with a different frequency. Filters work by absorbing certain wavelengths whilst letting others through, like sunglasses blocking UV.
An opaque object's colour depends on which wavelengths it reflects back to your eyes. A red apple absorbs all colours except red, which bounces back. White objects reflect everything, black objects absorb everything (which is why they get hot in sunlight).
All objects emit and absorb infrared radiation constantly. You're literally glowing with infrared right now! The hotter something gets, the more infrared it pumps out. Black surfaces are brilliant at both absorbing and emitting radiation compared to shiny or pale surfaces.
Here's the clever bit - any object at constant temperature absorbs and emits radiation at exactly the same rate. If it absorbed more than it emitted, it would heat up. Perfect black bodies would absorb absolutely everything that hits them, making them theoretical super-emitters too.
Cool Fact: Earth acts like a black body, constantly balancing the solar radiation it absorbs with the infrared it emits back to space.
4
of 5
5
of 5
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Physics57 views·Updated Jun 16, 2026·5 pagesUnderstanding Electromagnetic Waves
S
Savio Siby@avioiby_4nm7u9tda5z6
Ever wondered how your phone connects to WiFi, how X-rays see through your skin, or why microwaves heat your food? It's all down to electromagnetic waves - invisible energy that travels through space at the speed of light. These waves...
1
of 5
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Electromagnetic Waves: Production and Dangers
Electromagnetic waves are created when atoms or their nuclei change energy states. Think of gamma rays shooting out from radioactive atoms, or radio waves being generated by the electrical circuits in your phone when you stream music.
Radio waves work through oscillations in electrical circuits - basically electricity wiggling back and forth really fast. Your TV aerial picks up these waves and converts them back into electrical signals with the same frequency. It's like a wireless electrical connection!
Some EM waves are properly dangerous though. Ultraviolet waves, X-rays and gamma rays can seriously damage your body tissues. We measure this danger using radiation dose in sieverts (Sv) - basically how much risk you're exposed to.
UV rays are sneaky - they make your skin age faster and increase skin cancer risk. X-rays and gamma rays are even worse because they're ionising radiation. This means they can knock electrons off atoms, messing up your DNA and potentially causing cancer. That's why radiographers hide behind lead screens during X-rays!
Key Point: The higher the radiation dose in sieverts, the greater the risk to your health - but don't panic, everyday exposure levels are incredibly low.
2
of 5Sign up to see the content. It's free!
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EM Wave Applications and Properties
Radio waves power your Bluetooth headphones, TV broadcasts, and can even bounce off the atmosphere to reach places directly blocked by mountains. Microwaves don't just heat your dinner - they also carry WiFi signals and communicate with satellites because they pass straight through the atmosphere.
In microwave ovens, the waves make water molecules vibrate rapidly, heating your food from the inside out. Infrared radiation is basically heat energy - thermal cameras detect it to see in the dark, and all objects emit it (hotter things emit more).
Visible light travels through fibre optic cables as pulses, carrying your broadband internet at light speed. The light bounces along the cable's length like a game of ping-pong. X-rays can pass through soft tissue but not bone, making them perfect for seeing fractures.
All EM waves can be reflected, refracted, absorbed or transmitted depending on what they hit. Understanding these properties helps explain why your WiFi struggles through thick walls but radio waves travel for miles.
Remember: Different EM waves interact with materials differently - that's why we use specific types for specific jobs.
3
of 5Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Light, Colour and Infrared Radiation
The tiny slice of EM spectrum you can actually see gets split into different colours - each colour is just light with a different frequency. Filters work by absorbing certain wavelengths whilst letting others through, like sunglasses blocking UV.
An opaque object's colour depends on which wavelengths it reflects back to your eyes. A red apple absorbs all colours except red, which bounces back. White objects reflect everything, black objects absorb everything (which is why they get hot in sunlight).
All objects emit and absorb infrared radiation constantly. You're literally glowing with infrared right now! The hotter something gets, the more infrared it pumps out. Black surfaces are brilliant at both absorbing and emitting radiation compared to shiny or pale surfaces.
Here's the clever bit - any object at constant temperature absorbs and emits radiation at exactly the same rate. If it absorbed more than it emitted, it would heat up. Perfect black bodies would absorb absolutely everything that hits them, making them theoretical super-emitters too.
Cool Fact: Earth acts like a black body, constantly balancing the solar radiation it absorbs with the infrared it emits back to space.
4
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of 5Sign up to see the content. It's free!
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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?
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Students love us — and so will you.
4.6/5App Store
4.7/5Google 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 SiOS 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 KlichAndroid 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.
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