Waves exist all around us in our everyday lives. Understanding the physics of waves has allowed humans to create incredible technologies that make our lives easier. Many technologies use different types of waves in order to send and receive information. Follow along as Sal explains the different types of waves involved in the use of a cellphone. Created by Sal Khan.
- [Narrator] We've already learned a lot about waves and now we're going to connected to the bit to technology, especially the technology that most of us use most frequently and that's our cell phone. So pause this video and think if you can list all of the waves that your cell phone has to utilize or deal with or generate waves. All right, so the first thing that some of you might have realized is that your cell phone has to deal with sound waves. So you have sound traveling through the air. Your phone has to detect that sound. And then in most cases, it needs to digitize that sound. And we did other videos where we talked about sampling sound waves so that you can store it as digital information. And then depending what's happening, that detection is going to happen with your microphone. And if you were recording something, say recording a video or recording an audio file that digitize sound wave would then be stored. And then if you wanted to play it back, it would have to be turned back into a sound wave, which could then be emitted by your microphone. Now, it could also be that you're on, let's say a video call or you are having an actual phone call, the original purpose of phones. And so then that digitized information is going to be transmitted to a cell tower that could be tens of miles away. And I always find that amazing because the cell phone really has, it doesn't transmit in a particular direction, it kind of transmits in every direction. So it's got to be pretty powerful to get to that cell tower that might be around five or 10 or even more miles away. And then of course, if you're having a conversation, that cell tower is transmitting electromagnetic waves in a bunch of different directions. And then this cell phone says, "Hey, that's the signal for me." And it can take that digital information. And then it could use that to generate a wave pattern, which is then emitted by the microphone again, which you'd then hear. So sound waves is clearly a big part of what's going on with a lot of technology, not just cell phones, obviously. If you have a stereo system, if you have a television, sound waves are heavily utilized, or at least you have to deal with them. Now, what other type of wave? Well, you might be saying light waves, which would be correct, but I'm gonna generalize a little bit more and say, electromagnetic waves of which light waves are a type of electromagnetic waves. How do you use light waves? Well, a modern smartphone or cell phone will have a camera. And so it needs a way to detect light waves. So it will detect them and once again, it will digitize, it will store and then of course, it has this nice big screen here. So it needs a way to take that digitized information and then generate light waves. Every pixel on the screen can generate different frequencies of light waves or at least give the appearance altogether of generating different frequencies of light waves. Now, light waves are not the only type of electromagnetic wave. We've talked about having to communicate with a cell tower that could be 5, 10, 15, even further miles away. Well, those waves it's using to connect with your cell tower, those are radio waves, which are another type of electromagnetic waves. Now, are we done? Well just to make sure we can look at this little key here that you see at the top of a cell phone, and you could see that cell signal that tells you how good of a radio signal it is getting from the cell tower, but you can also see this Wi-Fi signal here. So Wi-Fi uses different frequencies of radio waves to communicate with the local network wherever you are. But once again, that is more radio waves. So I will let you go. I encourage you as you learn anything in any topic. Always look at the world around you and see how these concepts that you're learning in school or that you're learning in, say a Physics class are connected to things you do every moment of your life.