All Questions
Tagged with electromagnetic-radiation estimation
34
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1
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How many photons pass through us every second?
I just read this answer https://physics.stackexchange.com/a/229374, which says that, when a magnet rotates, photons are emitted with wavelength $λ=c/f$, where $f$ is the frequency of rotation. And ...
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4
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Accelerating Expansion of Universe - Why Not Caused by Radiation?
As I understand it, dark matter and dark energy are used as an 'explanation' for how universe expansion is accelerating; because without it gravity would be expected to cause a long term shrinking.
...
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139
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2
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How many photons are received per bit transmitted from Voyager 1?
As of 2024, according to https://voyager.jpl.nasa.gov/ , Voyager 1 is around one light·day away from Earth and still in radio contact. When Voyager 1 sends messages to Earth, roughly how many photons ...
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2
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Are these levels of RF radiation harmful?
I live on the top floor of a building that has four 5G antennas on the roof. The house is curved, and from my viewpoint, I can partially see one of the antennas pointing towards me. Curious about the ...
- 103
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4
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If microwave ovens run at 2.4 GHz, what is the long-term effect on living tissue of exposure to this frequency, but with a thousand times less energy?
Very low power electromagnetic waves with a frequency of 2.4 GHz can't cook anything. That's obvious, despite the heating effect such radiation has on water.
However, what if such an object containing ...
10
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1
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What fraction of the universe's energy is contained in photons?
From each point in the universe, the light of billions of stars, galaxies, supernovae etc. can be detected. So there seems to be a lot of energy/momentum "in flight".
Is it possible to ...
- 347
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How much radiation on the surface of the moon during a Coronal Mass Ejection (CME)?
I'm writing a book set on the moon. A Coronal Mass Ejection (CME) as large as the Carrington Event hits it. Three astronauts are caught out during an EVA. They will cover their rover in regolith to ...
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Does 5G affect your physics experiment?
Our institution wants to lease a nearby roof for a 5G mast. Has anyone experienced the installation and operation of telecoms infrastructure - particularly 5G - significantly affecting physics ...
- 537
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233
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How much UVA and UVB is blocked by shadow or being indoors?
I could not find a clear answer online so I though to try this forum instead.
I did find answers on how different types of glass can block different degrees of UVA and UVB. But I was wondering, if I ...
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2
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On which speed the relic microwave background radiation becomes dangerous for the people on space ship?
If we travel with speed close to the speed of light, the light waves becomes shorter and their energy increases (because we flight through much more light for the same time).
So, even background ...
- 768
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5
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Theoretically, could radio waves carry enough energy to destroy bacteria or viruses by resonance?
I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
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2
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Should larger rocky planets eventually crack due to temperature differences between their inner and outer layers?
Should larger rocky planets eventually crack due to temperature difference between their layers? When a tick piece of glass is left to cool down it would eventually crack...but this is caused ...
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1
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2
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543
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Does home cooking induction stove produces any harmful (to humans) electrical/magnetic fields?
An induction cooker, or stove that are based on the principle of electromagnetic induction, and is used much, for cooking food now a days.
My stove had a thick iron circular plate on the top.
Assuming ...
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34
votes
4
answers
10k
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Stood in front of microwave with the door open [closed]
I was cooking something in the microwave and opened the door early to check on it and the microwave didn't stop. I didn't realize this for a few seconds and when I did I shut the microwave off but I'm ...
- 467
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4
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514
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Can you shake a charged object fast enough to create light?
Electromagnetic radiation (a photon) is generated by an oscillating charged particle. Therefore, is it possible to vibrate an object at say 585 THz and create a green light source?
Alternatively: what'...
2
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3
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247
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How much watts per square meter does Phobos receive from Mars?
Being so close to Mars, Phobos should receive a non-negligible amount of irradiance from Mars. Be it from reflected sunlight, Mars' emitted infrared radiation, or other factors. I have no idea how to ...
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How much energy from the Sun could we get if we use Jupiter as a gravitational or atmospheric lens?
How much energy (watts) from sunlight could arrive to the focal point if we use Jupiter as a gravitational lens? and if we use it as an atmospheric lens by using refraction?
How far the focal point ...
user277436
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1
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What if static electromagnetic field is turned off? (in vacuum)
Lets assume that there is static electromagnetic field that has $E=17mc^2$ and $p=8mc$.
At some time $t=t_0$, the field is turned off. (e.g. the electric current of coil went to zero by resistance, ...
- 254
2
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3
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734
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Why viruses cannot be seen?
With the coronavirus pandemic, a lot of websites are publishing articles about viruses. In particular, I've seen some of these stating that viruses cannot be seen because they are so tiny they cannot ...
- 585
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Calculate irradiation from a LED lamp
I am working with cell culture and I want to irradiate a 96-well plate with a single color led lamp (let's say the peak is at 450nm). It's just a test, so a rough estimation would do.
I've been ...
- 11
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2
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Is the EMP threat to the power grid supported by physics? [closed]
Every once in a while I come across some article saying that our modern power grid could be knocked out of commission for up to a year by an electromagnetic pulse. I'm skeptical of such warnings.
...
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2
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What's the energy of all the light/electromagnetic radiation in our galaxy?
I came upon this question while watching a pop-sci video on youtube about Dark Matter and thinking about all the things that could be contributing gravitational influence to a galaxy.
From relativity ...
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Gamma Photons vs. Muons; Which is more expensive [closed]
Which one takes more energy to produce?
I ask as I theorize that keeping the plasma in a fusion reactor is very expensive.
Muons, while useful, are too short lived.
Maybe... Keeping the plasma at ...
75
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13
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44k
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If visible light has more energy than microwaves, why isn't visible light dangerous?
Light waves are a type of electromagnetic wave and they fall between 400-700 nm long. Microwaves are less energetic but seem to be more dangerous than visible light. Is visible light dangerous at all ...
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1
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Blocking WiFi with Faraday cage [closed]
As part of a project I'm trying to prevent WiFi transmission of frequency 2.4 GHz from reaching a Raspberry Pi via a Faraday cage.
Would a 20 micron aluminum foil do the job?
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2
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Would my house's wall stop gamma rays?
I'm wondering if there is a material which is able to stop all the electromagnetic spectrum's radiations. Something able to stop every electromagnetic radiation from the ones with the lowest frequency ...
8
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2
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Would a major electromagnetic pulse (EMP) leave most cars operable?
According to C. Davis of the Ask a Prepper blog, after a major electromagnetic pulse:
Most electronics will be fried beyond repair and it will be years – in some cases decades – before anyone is ...
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1
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545
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Why do planets not radiate EM waves in their orbits?
Despite being overall near-netural, I would expect the individual electrons and proton to radiate long EM waves as we accelerate around the Sun or rotate around our poles. Is the acceleration so small ...
- 163
15
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3
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616
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Can the question of a gravitationally accelerated charge radiation be tested experimentally?
I know that the question of radiation from a gravitationally accelerated charge has been discussed extensively at Does a charged particle accelerating in a gravitational field radiate?. Yet the ...
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21
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4
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9k
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Can lasers lift objects?
I have been fascinated by a very intriguing question - Can lasers push objects up?
Let's say we have a $1000~\text{mW}$ laser and we would like to lift an object of weight $100~\text{g}$.
By ...
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2
answers
5k
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From how far away could Earth's telescopes detect Earth-like radio signals?
The Earth has been broadcasting human generated radio signals for about 100 years now. If a nearby civilization were broadcasting similar radio signals, could we detect them with our own radio ...
- 7,165
42
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4
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6k
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How far out from the Sun is visible light still sufficient to read a book?
Recent pictures from the New Horizons spacecraft, shown below, seem to indicate that, at Pluto's distance, we are entering a twilight zone, with a distinct lack of colors, although that could be due ...
user81619
29
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3
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7k
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How many X-rays does a light bulb emit?
I read somewhere that most things1 emits all kinds of radiation, just very few of some kinds. So that made me wondering whether there is a formula to calculate how many X-rays an 100W incandescent ...
- 621
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1
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188
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Can extraterrestials detect our messages?
We transmitted several messages to the space and listening to space for signs of intelligent life for years (SETI).
Assuming they have at least the same technology we have, could they detect these ...
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