Would you expect effects due to the photon nature of light to be generally more important at the low frequency

Question

Would you expect effects due to the photon nature of light to be generally more important at the low-frequency end of the electromagnetic spectrum (radio waves) or at the high-frequency end (x rays and gamma rays)? Why?

I think the answer is the high-frequency end but I don't know how to explain why the low-frequency end is not the right answer. Please help me!

Answer 1

The terms used (radio waves, x-rays, gamma rays, etc...) should give you a strong hint of the answer. It's the higher frequency photons for which the photon nature is more important.

The main reason is how they interact with matter - i.e. how they are emitted and detected.

At low frequencies, the individual energies of each photon are very low and signals are typically detected (and emitted) due to the oscillating electric field of the waves. In other words, we use antennas for the job and we treat the signal as one big wave rather than a series of individual interactions.

At higher frequencies, it is the energy itself that is important, because events are typically single-photon. The photoelectric effect is a good example of this - photons hit a metallic surface and eject electrons from the surface. If the frequency of the light isn't high enough (that is, the energy of each photon isn't high enough), you don't get any electrons ejected no matter how intense the light is. If it is high enough, making the light more intense means more electrons get emitted (again - these are single-photon events, if there are more photons, there will be more emitted electrons). Most other situations are similar - the energy of single photons will cause a chemical change in the eye, single x-rays pass through the body and are detected one at a time, light-emitting diodes have a certain colour because that is the energy of one transition in a LED crystal.

So the basic answer is at low frequencies you detect the electric field, which can simply be added for all the photons, and at high frequencies you detect the energy, which can't be added because the interactions occur individually.

Answer 2

It really depends on what you consider important. Visible light ranges from 300-700 nm. Anything greater than 700 nm tends to  be microwaves, radio waves, etc. These types of electromagnetic waves tend to be used for electronics/technological communications. On the other hand, 300 nm is near the UV range. UV light is needed by the human body to produce Vitamin D which acts in bone matrix formation. So you can't really do without either.

Answer 3

I agree with srjh!

Higher energy means "more particle-like"

Lower energy means "more wave-like"

At least in terms of our interactions/observations of them.

Answer 4

The energy of a photon of light is given by:

E = hc/λ

Where h is Planck's constant, c the speed of light, and λ the wavelength.  The shorter the wavelength, the higher the frequency, the greater the energy.

Answer 5

The author intend that higher frequency reveals more of the particle nature. Examples are Phosphorescence (>1 eV), photoelectric effect(>1 eV), Ionizing radiation(>10eV), Compton scattering (>1keV),Pair production(>1 MeV) and other.

However this an example of anthropic thinking, and may be tied to both human physiology, environment, science and epoch.