# Tag Info

Accepted

### Light waves can't have a wavelength

You're right in saying that you can't always attribute a unique wavelength to an electromagnetic field. However, it's a simple consequence of Fourier analysis that you can write any field as a ...
• 3,804

### Light waves can't have a wavelength

Something does not need to be sinusoidal in order to have a wavelength. It just needs to be periodic or repeat after a certain distance. More generally, if $\lambda$ is the smallest non-negative real ...
• 2,569

### Light waves can't have a wavelength

Sahand gave a really great answer but I'd like to offer a different perspective. Edit: It was pointed out in the comments that energy conservation isn't enough to give periodic solutions. Which is ...
• 51

### Minimum frequency for a dipole antenna to work

As already remarked in the comments, the optimal frequency is based on the "1/2 wavelength" rule. But to what extent do things get worse at lower frequencies? To make this more ...
• 3,243

### Minimum frequency for a dipole antenna to work

No, but to maximize the radiated power at any frequency the dipole (horizontal, center-fed) must be 1/2 wavelength long. This means 5 meters at 30 megahertz, 50 meters at 3 megahertz, 500 meters at ...
• 94.4k
1 vote

### Could the increasing anisotropy of the universe lead to an additional blueshift?

It seems to me that what you are pointing out is related to what is known as the (integrated) Sachs-Wolfe effect, which has been considered in the missions that have measured the CMB anisotropies (...
1 vote

### Does the energy of a photon in comoving space change?

The energy of the photon decreases as the reciprocal of the scale factor. Typically, this can be interpreted as the wavelength being "stretched" by the expansion, but alternatively you can ...
• 132k

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