# Tag Info

47

First, a little bit of background. Transparency is not an absolute property of a material. Every substance is opaque, so long as light has to pass through enough of it, and opacity also changes according to ambient conditions. Some substances, such as most metals, are opaque even in $100\ \mathrm{nm}$ thin films, while many gasses will let a small amount of ...

27

Heating water on a hot plate is safe, because the hottest point is at the bottom of the pot. A lot of relatively small bubbles appear there without much overheating of the water, because there is a lot of nucleation at the uneven phase boundary steel-water. In a microwave, the hottest place is IN the water. The glass does not get heated by microwave (at ...

19

I'd separate transparent and colorless. Most gases are transparent or very nearly so because the concentration is low and absorptions are often weak. Chlorine, though is yellow-green, and has a noticeable color (from Wikipedia) Other halogens such as bromine and iodine do have observable colors as vapor, although as mentioned in the comments, you often ...

16

The amount of X-rays absorbed by an element depends on the size of its atoms (its absorption cross-section, specifically, as affected by the size of core orbitals that contain electrons that can be excited by X-ray absorption, and the number of electrons in those orbitals) and how many atoms are packed into a given volume. Big atoms that are close together ...

14

The mode of heating of a water glass in a microwave and on a stove is actually very similar. While it's true that microwave radiation penetrates somewhat into the body of water, the penetration depth is rather small. The main problem is that on a stove, you get uniform heating from the bottom, with temperature usually far higher than the boiling point of ...

14

An ammonia maser qualifies as an inorganic RF-emitting reaction. As the nitrogen changes position in the $\ce{NH3}$ molecule, ~24 GHz radiation is emitted. Similarly, organic methanol, $\ce{CH3OH}$ makes a maser found in nature, emitting at ~36.2 GHz and also at ~6.7 GHz. BTW, if the reactants are moving away rapidly (e.g. interstellar gases), visible ...

12

Very technically? Yes. Realistically? The probability is small enough that even if it does happen, the peaks for the multiple transitions are going to be small enough that we cannot really observe them on the spectrum. The lifetime of a given excited state is so small compared to the analogous time in the ground state that it can basically be considered ...

11

Microwaves dont have more energy, they just resonate at the frequency that causes molecular bonds to rotate. This specifically applies to dielectric molecules, molecules like water that have electric dipoles. From Wikipedia: Water, fat, and other substances in the food absorb energy from the microwaves in a process called dielectric heating. Many ...

9

The formula $E=h\nu$ is for the energy of one photon. You have a mole of photons. You need to use a slightly modified form: $$E=Nh\nu$$ where $N$ is the number of photons, in this case \begin{align} N&=n\cdot N_\mathrm A\\[6pt] &=1\ \mathrm{mol}\times6.02\times10^{23}\ \mathrm{mol^{-1}}\\[6pt] &=6.02\times10^{23} \end{align} Note that ...

8

Microwaves don't have more "energy" than visible light per photon. But this is irrelevant in the case of a microwave oven. There are two reasons for this but the first one one (as described in the existing answer) is actually a distraction: microwaves are relatively efficient at exciting molecular vibrations so dumping their energy as heat in the object ...

8

The chemical property that creates colour is the ability to absorb light of a specific visible wavelength. There is more than one way to do this. Mostly colour is caused by the existence of electronic transitions in substances that match the energy of some wavelength of light so when light hits the substance, some is absorbed by exciting electrons from a ...

8

A microwaved glass of water will 'bump' if the glassware is clean and the microwave heating is uniform. The water has some tensile strength, so a bubble will not form at the exact boiling temperature without some nucleus (low surface tension due to a gas void in a boiling stone, for instance), so the liquid can become superheated. On reaching in for the ...

8

Your question seems to be about the ozone layer, but shows some misunderstanding. First, ozone, $\ce{O3}$, absorbs some "radiation", specifically electromagnetic radiation, e.g. visible light or ultraviolet light (UV), as do many other gases. This absorption is not the same for all wavelength ("colors"), but in the UV region peaks about 250 nm, which is a ...

7

The photoelectric effect is described by the following equation $$E_\mathrm{max} = h\nu - \mathrm{WF_M}$$ where $E_\mathrm{max}$ is the maximum kinetic energy of the electron escaping from the metal surface, $\nu$ is the frequency of the incoming photon and $\mathrm{WF_M}$ is the workfunction for the particular metal. The kinetic energies of all electrons ...

7

Different regions of the electromagnetic spectrum correspond to different atomic and molecular processes, each with one or more associated spectroscopies. Here is a general summary, with decreasing frequency/energy going from left to right: In order to excite a valence electron, the longest wavelength or lowest energy radiation is usually in the visible ...

6

Before going into the mechanism of this reaction, I suggest you look up free radical mechanism, as this reaction takes place through that. $\ce{Cl-Cl}$ bond in $\ce{Cl2}$ is weak enough to be broken by mere UV rays (present in sunlight), and hence they undergo homolytic cleavage (the resultant products are $\ce{Cl}$ atoms, not ions) to form two $\ce{Cl}$ ...

6

The description given in your question pretty much explains things. I would put it in slightly different words which may or may not help, which is that the x-ray photon induces a dipole moment in the atom (a field induced dipole) which then radiates and so the x-ray is scattered. This is pretty much what happens in scattering by visible photons and we must ...

5

From memory something like this has been used as a basis for isotope separation using intense $\ce{CO2}$ lasers to fragment molecules. A process of 'ladder climbing' takes place aided by the fact that the electric field of the laser is so intense that it can bring levels into resonance that would otherwise not be so. Hence ladder climbing is possible. Multi-...

5

I have heard that electrons absorb or eject photons when transitioning from one orbital to another. Is this correct? Not exactly. The atom as a whole emits or absorbs the photon. There is no reason to single out the electron versus the nucleus in such transitions. Can atomic nuclei eject photons? Yes there are two ways a nucleus in particular (as ...

5

The comments on the question discuss this may not be about chemistry. One could argue that colors are chemistry related because they are associated with chemical substances: like minerals, chlorophyl, rust, dyes etc. So colors seem to be properties of substances. And that's fundamentally wrong. Color is a function of the visual system of the viewer! If that ...

5

The ionization energy of $\ce{Fe^3+}$ to $\ce{Fe^4+}$ is 54.8 eV. The energy of typical gamma radiation is much higher (in the order of roughly some keV to a few MeV). Depending on the energy, the interaction of average gamma radiation with the affected electron is mainly due to Compton scattering.

5

Answer to a More General Form of Your Question The answer to the question Can gamma radiation make non-radioactive stuff radioactive? is yes, but only if the gamma ray has enough energy. "Enough" is different for all atoms but for most of the lighter ones it's over 2 MeV, and what basically happens if the gamma ray has so much momentum that when ...

5

Explaining the diffraction of a photon off of a crystal lattice quantum mechanically is the same as finding what momenta can be transferred to the photon by the crystal lattice. The simplest way to model this, as Ivan noted, is to describe the momentum states of a particle in this kind of potential as these are the momenta which can be transferred to the ...

4

First, remember that electrons cannot exist between principle energy levels (distances). In a flame, electrons from lower principle levels (n=1,2,3... etc) will be knocked up to higher principle levels from the absorbed energy. Electrons do not like to stay in this high energy state and will travel back down to their ground state, and in the process release ...

4

The Balmer series relates to the electronic transitions in the hydrogen spectrum. In other elements it only requires that the energy difference between different excited states corresponds to a wavelength in the visible spectrum. These will clearly differ depending on the effective nuclear charge of the elemnt concerned.

4

The answer to your question is yes, there are non-transparent gases, however, it depends upon the wavelength at which you are observing and how much gas you are looking through. At some wavelengths the gas is opaque at others transparent. The amount of light absorbed depends on its concentration, the path-length through which the light passes, and how ...

4

Electromagnetic radiation consists of electromagnetic waves (oscillations of the electric and magnetic field), whereas corpuscular radiation consists of actual particles. Certainly, wave–particle duality can make the distinction between waves and particles fuzzy. However, electromagnetic radiation (whether described as wave or as photons) is massless (its ...

4

Yes. See Photo-Fission in Heavy Elements (1947) Phys. Rev. 71, pages 3-10 : fission should be possible for all heavy nuclei which lie well beyond the minimum of the packing fraction curve, provided sufficient excitation is provided to produce the necessary deformation of nuclear fluid which precedes division of the nucleus. Such excitation ...

4

Sure - ethanol and methanol (among others) are listed here as being "high absorbers" of microwave energy.

4

Not every model is perfect. Rutherford's model suffered from the problem of electromagnetic radiation but answered important questions about the structure of atoms by showing the existence of a positively charged nucleus. Bohr improved on this by realising that if electrons could only have certain energies then he could explain other things such as the ...

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