20 minutes per week is probably accurate for how much a person keeps a phone right next to their head these days. It’s not for device usage.
That explanation makes a lot of sense.
EDIT: I also know we aren't dealing with "spheres", but... I get the gist. Dipole antenna emits in this weird doughnut shape, but as a 3-dimensional object, we can estimate it to be kinda-sorta like a sphere :-)
Actually though, I think a sphere is still in a way the right object. The weird donut is a representation of the amount that is emitted in different directions - I guess it's a contour of equal intensity. But the radiation is still emitted at the speed of light in every direction. So the wavefront at any given time is a sphere (until it is defracted or reflected).
(Edited to add) unless you're thinking of a really big dipole, so you can't treat it as a point source? Or close to it.
> But the radiation is still emitted at the speed of light in every direction.
I think that makes sense.
> (Edited to add) unless you're thinking of a really big dipole, so you can't treat it as a point source?
Honestly, didn't think of that issue either. You're right though, some antennas (especially AM antennas) are the size of Godzilla, and its absurd to even think of them as point-sources.
The term gain is just referring to the antennas directionality relative to a perfect spherical omni radiator that doesn't exist.
We have many devices that emit 10Watts of EM radiation at us every day: we call them light bulbs or LEDs. Cell phones are only allowed to emit 3W IIRC.
It wouldn't surprise me if the screen has more EM than the radio.
LEDs and light bulbs do not emit modulated microwaves. If the screen emitted substantial RF radiation, the FCC (and related agencies in other countries) would have something to say about it.
Least-dangerous -- Radio / Infrared / Visible Light / Ultraviolet / XRays / Gamma Rays -- Most energy/dangerous
All light-bulbs, screens, LEDs (etc. etc.) emit visible light. There's a couple of bands in there that might be more dangerous than others (ex: Microwaves specifically resonate with water), but for the most part, Gamma Rays are the most dangerous, and Radiowaves have the least effect on our body.
Just hoping to pique your curiosity into the field of biology and away from hyper-reductionistic physics models.
You're begging the question.
You could have more easily stated your opinion as "low frequency radio waves disturb cells". Which is fundamentally false. There are lots of radio-waves being used around the world: RADAR systems, Radio-headquarter units... as well as people who live nearby radio-towers (TV, AM Radio, FM Radio), and cell phones.
Do you think WW2 units fielded with SCR-300 (World War 2 backpack radio) had increased amounts of cell membrane damage associated with them?
https://upload.wikimedia.org/wikipedia/commons/c/ca/Scr300.p...
Experiments with E-M effects on biology show that changes in current matter more than steady current. So, the effect of pulses could be larger than if it actually were transmitting full-time. We just don't know.
Are you claiming a heating effect or something else?
In fact all varying E-M fields induce electrical currents where they are absorbed. The effects of those electrical currents vary in myriad ways, depending both on the currents and on where they are absorbed. In living matter the currents are carried by motion of ions in solution. Not coincidentally, life is conducted largely by motion of ions in solution.
Incidentally the ADC's that sample the input dissipate the electrical energy captured by the antenna as heat however little it may be as is the case with all electrical circuits that sink electrical energy. So yes your cellphone does use a "heating effect" because where else does the energy go? Do you think it charges the battery or emits light with the captured energy?
It is not the heat, at the end, that makes your phone work. You may read up on how antennas work, if you care to have any actual, you know, facts. I promise it won't say one word about heat.
I know someone who needs to read up on antennas and digital receivers and its not me.
I never heard that, and looking at the list in https://en.wikipedia.org/wiki/Analog-to-digital_converter#Ty... I can't find any that work this way.
Radio receivers do not depend on an analog to digital converter, or even a resistor, to extract a signal from an antenna. The essential component is a diode.
(That is not to say that, having detected, amplified, and demodulated an antenna signal, the result won't finally drive an A/D converter; you can drive anything you want to after all that. Even a speaker. But operation of the speaker, too, does not depend in any way on heat.)
Even in a analog receiver the power amplifiers used to drive a speaker or whatever are going to dissipate the signals power as heat in order to modulate the amplifiers output power (out power will always be less than power supply power).
If you are talking about a crystal radio, then yes the input power drives a speaker and is turned into sound instead (along with some power lost heat in the circuits resistance).
The capacitor is discharged using a resistor of known value.
Also take it down to the comparator level which basically all ADC use the op-amps use transistors and resistors and are themselves dissipating the input power in order to measure voltage.
The word transistor is a contraction of transfer resistance, they are electronically variable resistors and as everyone knows dissipate power as heat during function.
A) The main method that use a ADC to work is heating a resistance and then measuring the temperature or the time to cool down or something like that. [1]
B) As a side effect of the internal working, the ADC produce heat. The heat is not important for the operation, but it's an inevitable side effect.
My opinion: A) No, B) Yes
Can you both please answer A) and B) with "Yes" or "No"?
[1] Note that something similar is used to measure pressure https://en.wikipedia.org/wiki/Pirani_gauge .