In the electromagnetic spectrum, as frequency increases, at what point do photons start being detected? And further beyond the ultraviolet, are they still photons? Are photons detected in the microwave region for example? How is light being the defined without photon action?

 

Bob.

its always photons. from zero hertz(well, as close as is possible) to infinite hertz(as close as is possible.)

Anytime you have a situation where you detect a single quantum of energy, it's a photon. Classically, it's an oscillating electromagnetic field.

 

I seem to recall a discussion which confirmed the longest wavelength of a single-photon detection, but I can't find it ATM.

insane_alien,

 

Concerning your reply,

 

At what point are these other frequencies responsive to optics such as a prisms or lenses?

 

We know radio frequencies respond to surfaces and their contours such as parabolic dishes, and aircraft shapes, but where in the spectrum is the transition point where they start to respond to transparent optical materials.

 

We know some materials are transparent to some frequencies, but opaque to others; the atmosphere being the example.

 

Bob.

The visible part of the electromagnetic spectrum is in the frequency range from about 4×10¹⁴ Hz (red) to about 8×10¹⁴ Hz (violet), if that’s what you mean.

bob, they always undergo optical effects. it's just that for some frequencies most materials have such a low refractive index that to construct a lense would require such an immense size as to be impractical.

bob, they always undergo optical effects. it's just that for some frequencies most materials have such a low refractive index that to construct a lense would require such an immense size as to be impractical.

 

You could try playing "swat the photon", by moving a lens fast enough toward it.