All Questions
Tagged with electromagnetic-radiation energy
164
questions
-3
votes
0
answers
22
views
Is there an IR-camera-detectible color that can be the coat for a material to transfer the material heat by emitting into the space? [closed]
If we see a material it is coloured in a color that our brain could easly recognize. But when we look at it by the help of an IR camera it could also be coloured and if two materials have same ...
1
vote
0
answers
17
views
Will an electron release energy when it is added into an atom for which electron affinity value is negative (endothermic)?
According to my understanding, when an electron is added into an atom, it emits energy in the form of photons because it is a form of de-excitation or relaxation. This is when electron affinity will ...
- 11
1
vote
1
answer
312
views
How to get the formula of the energy of EM waves?
I am trying to get the formula for energy of EM waves:
$$W = \frac{E^2 + B^2}{2}$$ calculating the work done on a test charge by the force: $$\mathbf F = q(\mathbf E + v \times \mathbf B)$$ $\mathbf ...
CommunityBot
- 1
0
votes
0
answers
36
views
What is the solar radiative power on a clear sky day through a surface which is parallel to the sun's incidence on Earth?
Assuming that the solar power through the incident surface is known. How can we calculate or estimate the radiation through the parallel surface assuming a clear sky?
Looking for watts per square ...
- 111
6
votes
3
answers
12k
views
Is the energy of a photon continuous/discrete?
I was struggling today with this question: does a free photon have a continuous energy spectra?
Free means in no context of any energy system (eg. an atom, em field). Although I'm asking myself if ...
- 207k
0
votes
1
answer
205
views
Ionizing radiation energy in joules
The energy level at which radiation can be labelled as ionizing is about $10.00-33.85$ eV. This (the $33.85$ eV) is equivalent to $5.423368\cdot 10^{-18}$ Joules. In terms of joules this is a very low ...
CommunityBot
- 1
2
votes
2
answers
207
views
Does the formula $E = hf$ apply to all electromagnetic waves?
The formula $E=hf$ shows the energy contained in one photon. Here, we use the simple half wave dipole antenna to evaluate the energy of photons at different frequencies. Surprisingly that gives a ...
CommunityBot
- 1
1
vote
1
answer
32
views
Absorption and emission spectrum
I was wondering how do you see a spectrum when light is passed through a substance. Like most of the substances we use are opaque, so how does light pass through them without being reflected? Also ...
- 3,202
2
votes
1
answer
36
views
Why don't the delocalised electrons in a metal emit light when they hit an atom and change their velocity very quickly (i.e. accelerate)
We know that in metals there is a sea of delocalised electrons which can freely travel around the lattice of metal ions and that these delocalised electrons move around at large speeds, sometimes ...
- 21.9k
0
votes
2
answers
3k
views
Relationship between Stefan-Boltzmann Law and Radiance
In a textbook, the equation for radiance is given
I am struggling to understand the relationship between the two equations. From what I know, multiplying the value obtained by the Stefan-Boltzmann ...
- 135
0
votes
2
answers
49
views
Can a region of electromagnetic waves alone be considered a thermodynamic system? Can work and heat interactions be made sense for them?
Consider an ideal antenna producing coherent radio waves, and suppose the waves are not received by any body (they are sent off to space). Can we say a work interaction/transfer has been done? Or is ...
- 39k
10
votes
1
answer
1k
views
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 ...
- 6,404
1
vote
2
answers
295
views
Why does work done by light not equal energy absorbed?
Question: Suppose a spherical particle of mass $m$ and radius $R$ in space absorbs light of intensity $I$ for time $t$. (a) How much work does the radiation pressure do to accelerate the particle from ...
CommunityBot
- 1
2
votes
1
answer
43
views
What happens to light absorbed by a body with color?
As everyone knows, an object with color appears that way because it reflects its specific color(s). Textbooks tell us other colors are absorbed. Now, here's the question: what happens to the absorbed ...
- 6,112
-1
votes
1
answer
127
views
How big is light pressure as a fraction of light energy?
Light hitting a surface impart a force on the surface, often called "radiation pressure". My question is, given a perfectly reflective surface, if light hits it at 90° to return in the ...
- 207k