2
$\begingroup$

enter image description here

In this photo you can see part of the bowl, which I turned upside down and placed on top of various electromagnetic sources to determine whether the waves could pass through it. The graph in the background illustrates my results.

For the shorter wavelengths, I had to guess. I knew that ultraviolet would be blocked, but I assumed that x-rays and gamma rays could go through the bowl.

To me, is seems that wavelengths in the range of, say, 100nm to 900nm are more easily stopped by the bowl. Even though I used a metal bowl, I think a plastic or paper bowl would produce similar results.

So my question is: why are the waves in the middle of the spectrum stopped by the bowl and not those at the ends?

Here are some of the items I used in my experiment: a TV Remote, a Bluetooth device, an IPhone, our Home WiFi, a Cellular LTE, a Sprinkler Remote, and a Radio.

All of the items on my list were able to pass through the bowl except the TV remote, which I assume was infrared.

Improve this question
$\endgroup$
11
  • $\begingroup$ Radio waves and microwaves will NOT pass "through a dog bowl", if it is made, as it appears, from aluminium or any other conductive material. $\endgroup$
    – ProfRob
    Commented Dec 6, 2016 at 14:47
  • $\begingroup$ It does. The cell phone works under the metal bowl. Try it. $\endgroup$
    – Lambda
    Commented Dec 6, 2016 at 15:53
  • $\begingroup$ Stream music or any other sound onto your phone from a wifi network. Wrap the phone in aluminum foil, one layer, and it will still work well beyond buffering time. $\endgroup$
    – Lambda
    Commented Dec 6, 2016 at 17:43
  • $\begingroup$ I did the demo this morning in my lecture - the same one I do every year. A mobile phone does not work (will not receive phone calls) when wrapped in aluminium foil. Ditto a radio wrapped in a single sheet of aluminium foil. Do the Math. $\endgroup$
    – ProfRob
    Commented Dec 6, 2016 at 18:26
  • 1
    $\begingroup$ it passes under the bowl... You have to realize the extreme optimization of the channel capacity that is engineered into modern cellphones. They do a lot even in unfavourable conditions. $\endgroup$
    – G. Bergeron
    Commented Dec 11, 2016 at 11:41

1 Answer 1

Reset to default
2
+50
$\begingroup$

Long-wavelength and short-wavelength radiation passes for different reasons: long-wavelength does not actually pass, but bends around the bowl due to diffraction (or is reflected from the walls), as the wavelength is greater or of the order of the dimensions of the bowl, and short-wavelength radiation passes because its frequency is higher than the plasma frequency of the metal of the bowl. Plastic and paper can give very different results (for example, in the visible range, if the plastic is transparent).

Improve this answer
$\endgroup$
3
  • $\begingroup$ I awarded this answer my bounty because time was out and it was the only answer. The visible portion of the spectrum appears to be the easiest to stop, but it's still not clear to me why. $\endgroup$
    – Lambda
    Commented Dec 13, 2016 at 4:33
  • $\begingroup$ @Lambda: as I said in the answer: because the visible light cannot pass directly through the bowl (its frequency is lower than the plasma frequency of the metal of the bowl) and cannot pass around it using diffraction (as its wavelength is much less than the dimensions of the bowl). $\endgroup$
    – akhmeteli
    Commented Dec 13, 2016 at 4:55
  • $\begingroup$ @Lambda: You asked: "Is there a formula that explains how "durable" an electromagnetic wave is?" It's difficult to write down all the relevant formulas here: propagation of electromagnetic waves is a complex phenomenon. Some of the aspects of this phenomenon are plasma frequency, diffraction, skin-effect. You may wish to look them up. $\endgroup$
    – akhmeteli
    Commented Dec 13, 2016 at 5:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.