All Questions
Tagged with electromagnetic-radiation wavelength
206
questions
146
votes
8
answers
281k
views
Why does a remote car key work when held to your head/body?
I was trying to unlock my car with a keyfob, but I was out of range. A friend of mine said that I have to hold the transmitter next to my head. It worked, so I tried the following later that day:
...
- 2,239
54
votes
5
answers
9k
views
Are there any theoretical limits on the energy of a photon?
Is there any lower or upper limit on the energy of a photon? i.e. does the mathematical framework we currently use to study photons blow up when a photon surpasses a certain upper limit of energy? (or ...
- 7,319
41
votes
4
answers
191k
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Why does wavelength change as light enters a different medium?
When light waves enter a medium of higher refractive index than the previous, why is it that:
Its wavelength decreases?
The frequency of it has to stay the same?
- 4,607
40
votes
4
answers
13k
views
Is there an infinite amount of wavelengths of light? Is the EM spectrum continuous?
The electromagnetic spectrum is a continuum of wavelengths of light, and we have labels for some ranges of these and numerical measurements for many.
Question: Is the EM spectrum continuous such that ...
- 597
33
votes
7
answers
23k
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Radio antennas that are much shorter than the wavelength
From my limited experience with ham radio when I was a kid, I expect transmitting and receiving antennas to have lengths that are on the same order of magnitude as the wavelength, and in fact I recall ...
user4552
31
votes
12
answers
7k
views
Why is everything not invisible if 99% space is empty?
If every object is $99$% empty space, how is reflection possible? Why doesn't light just pass through?
Also light passes as a straight line, doesn't it? The wave nature doesn't say anything about its ...
- 435
25
votes
6
answers
129k
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Do all frequencies of light have the same speed?
Is there any speed difference between blue or red light? Is there ever a speed difference? Or do all types of light move at the same speed?
- 939
25
votes
3
answers
8k
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If energy is quantized, does that mean that there is a largest-possible wavelength?
Given Planck's energy-frequency relation $E=hf$, since energy is quantized, presumably there exists some quantum of energy that is the smallest possible. Is there truly such a universally-minimum ...
- 453
22
votes
3
answers
13k
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What is the minimum wavelength of electromagnetic radiation?
As a first approximation, I don't see how a wavelength of less than 2 Planck distances could exist. The question is: Are there any other limits that would come into play before that?
For example:
...
- 1,269
22
votes
5
answers
12k
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What exactly is meant by the wavelength of a photon?
I've been thinking about this for quite some time, and from looking online I haven't found a satisfying answer.
Lots of photons, such as visible-light photons have very small wavelength (which from ...
- 379
21
votes
5
answers
20k
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Why is it necessary for an object to have a bigger size than the wavelength of light in order for us to see it?
I keep hearing this rule that an object must have a bigger size than the wavelength of light in order for us to see it, and though I don't have any professional relationship with physics, I want to ...
- 313
20
votes
8
answers
5k
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What does the "true" visible light spectrum look like? [closed]
When I google "visible light spectrum", I get essentially the same image. However, in each of them the "width" of any given color is different.
What does the "true" ...
- 337
20
votes
3
answers
3k
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Is it possible to confine a photon in less than its* wavelength?
*(Its, or associated. That is somehow the question).
I can think of, at least in principle, a perfectly reflecting optical cavity with dimension comparable to the wavelength of the electromagnetic ...
- 1,729
18
votes
2
answers
43k
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How do you measure wavelength/frequency of light
I'm sure this is a trivial question for someone who knows something about electromagnetic radiation, but: how do experimenters measure the wavelength/frequency of light? For example, how do we know ...
- 4,576
17
votes
2
answers
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Why is Near Field Communication (NFC) range limited to about 20cm?
Near Field Communication (NFC) operates at 13.56 MHz.
Near Field is the region situated at a distance r << λ
λ = c/f
...
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