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  • DIANNA COWERN (VOICEOVER): This episode

  • of "Physics Girl" is supported by Squarespace.

  • Share your passion with the world.

  • Putting my phone in the microwave.

  • Do not turn it on.

  • Dianna Cowern.

  • All right.

  • It's in there.

  • [GASPS]

  • It's ringing.

  • Oh, definitely ringing.

  • Oh, look at that.

  • This was surprising to me.

  • The microwave let through a cellular signal.

  • My thinking before I did any research on the subject

  • is that a microwave should act like a Faraday cage.

  • The basic idea of a Faraday cage is

  • that, when an electric field or some electromagnetic waves

  • like those from a cell phone hit the enclosure,

  • they cause electrons in the metal to move and create

  • an electric field to exactly oppose and to cancel out

  • the external field.

  • So whatever's inside feels nothing.

  • I thought that microwave should act like Faraday cages,

  • keeping signals out and microwave radiation in when

  • you're cooking your food.

  • But this one obviously leaks.

  • So I had to try more microwaves.

  • Do you think it's going to rain?

  • OK, [INAUDIBLE].

  • I think it will.

  • DIANNA COWERN: You think it will?

  • And you're going to call me?

  • [RINGING]

  • Mm.

  • It's not ringing.

  • It's ringing.

  • Yeah, so it's not ringing.

  • Oh my gosh.

  • It's ringing!

  • How this is happening?

  • Now we have to figure out why this is.

  • It depends on the microwave.

  • I wanted to know why, but I was also really curious

  • what part of the microwave is leaking.

  • DIANNA COWERN (VOICEOVER): So we first

  • tested what I was sure would be a good Faraday cage.

  • DIANNA COWERN: Nothing?

  • KYLE: Two rings and voicemail, so I

  • don't think it went through.

  • DIANNA COWERN (VOICEOVER): Then we covered the whole microwave

  • door in aluminum foil.

  • DIANNA COWERN: This is what happens

  • to my friends' microwaves when they ask me to dogsit.

  • [CHUCKLES]

  • It's not ringing.

  • So it's leaking somewhere around the microwave door.

  • So microwave-- not a good radio wave cage.

  • DIANNA COWERN: Microwave.

  • Right.

  • DIANNA COWERN: Right?

  • Those are receiving microwaves.

  • Are they?

  • OK.

  • Time to figure out what frequency

  • of electromagnetic radiation cell phones and microwaves

  • are using.

  • That's what Kyle and I weren't sure about.

  • Because if microwaves are getting in at my phone,

  • is microwave radiation getting out while I'm cooking my food?

  • That's what we all want to know, right?

  • I'm Samy Kamkar.

  • In general, I call myself a hacker.

  • So you-- so this receives radio frequency signals.

  • This receives and transmits.

  • This device is awesome.

  • It measures and emits radio frequency signals

  • between 1 megahertz and 6 gigahertz.

  • Our cell phone and microwave radiation

  • should be in that range.

  • And we're using the gqrx software,

  • which is a spectrum analyzer, to look at a range of frequencies.

  • Samy first demonstrated the device to me with a car

  • key fob, which also emits radio frequency signals.

  • When I actually hold this down, we can actually see a signal.

  • We see two frequencies.

  • DIANNA COWERN (VOICEOVER): The numbers

  • show the range of frequencies you're looking at.

  • Above that is a live view of the signals in that range,

  • like these two peaks from the key fobs.

  • And down below, it records when you detected signals.

  • DIANNA COWERN: I don't know why it's so cool to see it

  • in graph form, but it is.

  • SAMY KAMKAR: It is so cool, because, yeah, you

  • know you can finally visibly see it, right?

  • So you just change it to 700, which

  • is one of the cellular frequencies.

  • So we have a phone call going on.

  • SAMY KAMKAR: Hello, hello, hello.

  • DIANNA COWERN: And every time we talk, you

  • can see some of the signals coming up.

  • Now, what happens to that signal when

  • we put my phone and the HackRF detector in a Faraday cage?

  • This is, like, legit.

  • Yeah, yeah, this is like a legit Faraday cage.

  • There is a match.

  • So if you look closely, that's a metal mesh.

  • DIANNA COWERN: All right, I'm going to put my phone in here,

  • and then I want to close it and see what happens to the data.

  • So--

  • SAMY KAMKAR: It's already way less.

  • DIANNA COWERN: Yeah, nothing.

  • My phone is still on, but it's not transmitting anything--

  • SAMY KAMKAR: Oh, interesting.

  • DIANNA COWERN: --with is interesting.

  • SAMY KAMKAR: So we're not seeing it trying to communicate.

  • DIANNA COWERN: Yeah.

  • SAMY KAMKAR: Right?

  • Just radio silence.

  • DIANNA COWERN: Yep, Faraday cage works.

  • So let's go up to 2.4, where we know

  • there's a bunch of [INAUDIBLE].

  • DIANNA COWERN: Yeah.

  • So we see-- we see blips.

  • DIANNA COWERN (VOICEOVER): And that's

  • where Wi-Fi is on the spectrum.

  • A common Wi-Fi frequency is 2.4 gigahertz.

  • So now we've seen what happens to the cell phone signal

  • when you put it in a real Faraday cage,

  • and we've gotten great measurements of that.

  • It's time to figure out what frequency microwave oven

  • radiation is.

  • But first--

  • The phone's in your microwave.

  • I think the phone call will not go through, because I believe

  • my microwave is awesome.

  • DIANNA COWERN: Let's see.

  • Moment of truth.

  • It's still not ringing.

  • AUTOMATED VOICE: Your call has been forwarded--

  • SAMY KAMKAR: Yes!

  • DIANNA COWERN: Can we try one more thing?

  • Because I actually haven't tried this yet.

  • On this experiment, I turned cellular frequencies off,

  • I turned Wi-Fi on, and I had Samy

  • call me through the Wi-Fi network on FaceTime

  • to see whether Wi-Fi signals get through.

  • FaceTiming now.

  • [PHONE RINGING]

  • Oh, look at that.

  • Wow, so 2.4 is still reaching through my microwave.

  • DIANNA COWERN: Which is interesting,

  • because Wi-Fi is closer to microwaves

  • that you use to cook your food.

  • Hmm.

  • Did you hear that?

  • One of the most surprising things about all of this for me

  • was that Wi-Fi uses 2.4 gigahertz,

  • and most microwave ovens use 2.45 gigahertz.

  • In fact, your microwave oven probably

  • says 2450 megahertz on it.

  • On older microwaves that leaked a lot more, and we don't have,

  • I think--

  • DIANNA COWERN: The regulations?

  • Yeah, as many regulations on that.

  • You would actually find that, let's say, older Wi-Fi would--

  • your Wi-Fi would just go out when

  • you would microwave something.

  • DIANNA COWERN: No way.

  • Checks out.

  • So there's just one more thing to try.

  • We're going to keep the spectrum on the same 2.4 gigahertz range

  • and see whether we can detect any microwave oven radiation

  • from outside the microwave.

  • SAMY KAMKAR: Three, two, one, start.

  • So now I'm going to stop.

  • Stopped.

  • DIANNA COWERN: Yep.