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1answer
46 views

How do electrons ever receive the amount of energy needed to move up energy levels?

Suppose there is a (blackbody) electromagnetic radiation source. It should emit a finite amount of photons every second with an intensity against frequency graph looking similar to a Maxwell Boltzmann ...
1
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1answer
35 views

What is Dipolar Dissipation?

When light hits an object, a part of it gets absorbed. Sometimes, people refer to that as "dipolar dissipation". What do they mean exactly by that and does it apply for all materials ? Thanks.
2
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0answers
51 views

Feynman’s Treatment of an Opaque Wall

First time poster. I’ve been reading Feynman’s Lectures on Physics, and I’ve just finished reading his treatment on diffraction. Feynman described a method of thinking about an opaque wall that was ...
-1
votes
2answers
102 views

If EM waves of radio range can pass through large obstacles, why antennas do receive them? [closed]

For example a tiny antenna in the phone, why em wave do not pass through it, but pass through concrete walls?
1
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1answer
398 views

Do objects reflect light of their own color based off constructive wave interference?

Note: Why objects reflect light of their color is already answered here: Physics of color: why do visible colors absorb all colors except the color itself? My question is whether my following theory ...
2
votes
2answers
317 views

Why are some materials dull rather than shiny (cloth, coal, matte paint etc.)?

The converse of this question is perhaps "why are metals shiny". From what I understand, metals are covered by a sea of free electrons that oscillate in response to incident light/EM wave, and the ...
1
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1answer
250 views

Why light cannot pass through wall whereas Sound can? [duplicate]

I have read answers stating that light is not able to be transmitted through a wall whereas sound is easily transmitted due to difference in wavelength. But, why? I am looking for detailed and ...
0
votes
2answers
814 views

Can light travel through solid substances such as wood?

Today as I was doing my science, I came across this statement: "In essence, then, the Special Theory of Relativity says that the speed of light is the ultimate speed limit because nothing can ...
2
votes
1answer
43 views

How do we detect infinitely narrow emission / absorption lines within continuous electromagnetic spectra?

This always bothered me, especially in the case of absorption lines. for instance, if you have a blackbody emitting a continuous spectrum, and then a filter in front that only filters out one very ...
2
votes
1answer
1k views

Why does the sun/moon appear red when there are fires?

Recently, in the United States, the moon and sun have become very deep red when they are near the horizon. The reason given for this is that there have been extensive wild fires in the Northwest. So, ...
15
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4answers
2k views

Why do colours of object change due to incident light?

A leaf is green, a pen is blue and so on because those objects absorb all colours and reflect only one colour. However when red light is incident on these objects, their colour becomes reddish. Why is ...
11
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3answers
810 views

Why don't absorption and emission lines cancel out in our Sun?

I was looking at this answer on why absorption lines and emission lines don't cancel out: An experiment shining light on the material and looking at the reflected spectrum will see absorption ...
0
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1answer
666 views

How do surfaces absorb or reflect light? Specifically, what is the physical process happening at the molecular level? [duplicate]

As an example, I know a leaf looks green because it absorbs red and blue light, but reflects green light*. My question is how the red and blue light are absorbed, not reflected. And conversely why the ...
2
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1answer
837 views

Why can X-rays pass through a human body unimpeded yet optical waves don't as they get scattered and absorbed?

Why is it that optical waves get scattered or absorbed when directed into a human body yet X-rays pass straight through the body? The only difference between them is X-rays have a smaller wavelength ...
1
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1answer
2k views

What is absorption rate of WiFi and Bluetooth RF in water? [closed]

Specifically, frequencies 5.75GHz and 2.4-2.485GHz. I want to place a hermetically sealed circuit at the bottom of a gold fish bowl, and want to know if the water will significantly attenuate WiFi or ...
0
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1answer
390 views

Cardboard allows AM/FM waves but NOT light - Why?

I am going through Electromagnetic waves. In footnote, the author was giving illustration on transparency of materials. Was going through some references here as well as in Google. Many people ...
0
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1answer
68 views

Absorption spectra of molecules library

Do you know where I can find a library with absorption spectra? I would like it if then I could input a wavelength and get back a specific value. More specifically I would like to see the absorption ...
4
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3answers
3k views

How do Black Bodies Absorb and Emit Radiation? [duplicate]

I have learnt how the gases of elements are able to absorb only certain wavelengths of EM radiation corresponding to the energy transitions between energy levels of orbitals. Furthermore, these ...
28
votes
2answers
5k views

Why do X-rays go through things?

I always heard that the smaller the wavelength, the more interactions take place. The sky is blue because the blue light scatters. So why is this not true for X-rays, which go through objects so ...
1
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1answer
102 views

Mie theory: Interpretation in terms of intensity

I'm trying to understand Mie theory. For this I'm reading the book "Absorption and Scattering of Light by Small Particles" by Bohren and Huffman. The derivation of the formulas is fine, but I'm stuck ...
3
votes
1answer
123 views

How much ionizing (carcinogenic) radiation is one exposed to on a commercial flight, what are the sources, and how could exposure be minimized? [closed]

I don't know if this is the best place to ask this question, but I figure a physics-based answer would be the most satisfying. I'd be happy to be convinced I'm being paranoid about protecting an ...
2
votes
2answers
469 views

Why does the light instantly disappear when we switch off the source?

For example i take a box which is completely covered by the most perfect mirrors possible inside and inside that box i have a bulb whose bulb holder is also covered with the most perfect mirrors ...
7
votes
1answer
912 views

Test whether a glass prevents you from getting your Vitamin D portion?

I work in an office with glass, which I believe filters the UV radiation of the sunlight. Is it possible to test if exposure to the light coming through the glass will supply Vitamin D for me as a ...
1
vote
2answers
429 views

Absorption of waves in a plasma

Suppose a plasma has characteristic frequency $\omega_p$. Since $$n = \sqrt{\left(1-\frac{\omega_p^2}{\omega^2}\right)} $$ For $\omega<\omega_p$, the refractive index will be imaginary - which ...
0
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2answers
275 views

Wave frequencies and barrier width?

I know a fact that says a wave can go through barriers thinner than its length. This is why for example FM radio can be picked anywhere while antenna TV needs direct sight to the transmitter. Is this ...
2
votes
1answer
255 views

some questions regarding Doppler shifting versus absorption-emission

I just got in what I thought was a silly exchange where a self-identified physicist states that the difference between "red-shifting" (in the Doppler sense) and the re-emission of light at longer ...
4
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1answer
754 views

Do higher frequency EM waves travel longer than lower EM frequency waves?

In radio communication, the distance traveling seems to be an important parameter before we choose the frequency band of communication. There is also a path-loss model that describes a distance $\...