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Course: High school physics - NGSS > Unit 6
Lesson 2: Electromagnetic radiation and matterEffects of different wavelengths of radiation
When electromagnetic radiation is absorbed by a material the energy it carries has to go somewhere. When lower energy waves, like radio and infrared waves, are absorbed there can be an increase in temperature of the absorbing material. Higher energy waves, like x-ray and gamma waves, can actually permanently damage or change materials. Learn about the different types of electromagnetic waves and how their energies can influence their effects on objects.
Created by Sal Khan.
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Video transcript
- We've talked about this in other videos. But just as a review, things like visible light, or the x-rays used when you
go to the doctor's office to see what's going on with your bones, or the microwaves used to heat your food, or the radio waves used for communication. That these are all really
the same phenomenon, which is that they are all different types of electromagnetic waves. And the main difference between them is their wavelength or their frequencies. We know that the longer the wavelength, the lower the frequency, and the shorter the wavelength,
the higher the frequency. Now, what's also interesting
about electromagnetic waves is that everything in the universe that has any temperature at all, which is most things in the universe, will emit electromagnetic waves. You might look at yourself
right now and say, wait, am I emitting electromagnetic waves? Well, you're probably not
emitting visible waves. You're reflecting visible waves, that's why you can see your hand. But your body is emitting infrared waves. Now, just as almost
everything can emit ways, waves can also be absorbed, depending on the material, depending on the size of the object. Now, generally speaking, when electromagnetic waves are
absorbed by some substance, it's turned into thermal energy. You can experience that, go outside on a sunny
day, wear a black shirt, and a black shirt is not
reflecting much visible light. And so it's all being absorbed, or most of it is being absorbed, and it gets converted to heat. You will get much hotter than a friend who is wearing a white t-shirt. Now, we have to be pretty careful as we get to higher
frequencies in visible light. Ultraviolet light, that's
what's causing sunburn. And the risks only increase as you get to higher frequencies, like x-rays, and gamma rays. What these really high frequency electromagnetic waves can do is knock out electrons from atoms, which would ionize them, which would change their
chemical properties. That could affect DNA. It
could affect other cell tissue. And so that's why it could cause cancer or just even kill cells
if they get strong enough.