Questions tagged [light]

Photons and electromagnetic radiation, primarily in the human-visible range. For the chemical effects of light, use [photochemistry].

Filter by
Sorted by
Tagged with
-4 votes
1 answer
46 views

Why can electrons absorb only certain frequencies and what happens if the energy keeps increasing? [closed]

Electrons can only absorb and/or emit those photons whose frequencies correspond to a certain line in the absorption or emission spectrum of the atom. It is an all or none case with photons and ...
0 votes
0 answers
168 views

Why wavelength of Rubidium flame test(red violet) is more than Lithium(crimson red)

My teacher show this table from my book Here, you can see Red violet wavelength is more than Lithium, which is against order of visible light which increase according to acronym 'VIBGYOR' According ...
2 votes
1 answer
47 views

Diffraction Derivation- relating the angle between deflected ray and original

This relates to diffraction from objects with a periodic structure. I’m trying to relate the psi angle (diffracted angle) to the theta angle (angle between diffracted ray and the original non-...
  • 39
2 votes
0 answers
55 views

Emission Spectra Light Wavelength Deviations for Mercury

The Problem: Inconsistencies between the measured and true values of mercury's spectra light wavelengths emitted following a laboratory experiment. What I Know: The experiment conducted was viewing ...
  • 29
9 votes
1 answer
693 views

Why does the same electron transition release photons of different frequencies for some elements?

Question: For elements in the same period with different numbers of valance electrons, why does the same electron transition release photons of different frequencies? Example: For valance electrons ...
1 vote
1 answer
97 views

How are photons converted into thermal energy?

I know when light strikes an object it excites electrons into higher energy states. I know thermal energy is basically just a lot of atomic and molecular kinetic energy. Does the excitation of the ...
  • 11
-1 votes
1 answer
71 views

Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles? [closed]

Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles(like 360°); as there won't be any deflection in the analyser of the polarimeter?
3 votes
0 answers
67 views

Calculate frequency dose from different light intensities

The quantum yield for homolytic O-O cleavage of (CH$_3$)$_3$COOC(CH$_3$)$_3$ at $266$ nm is $0.21$. In one experiment, a pulsed laser of this wavelength was used to induce the formation of t-butoxyl ...
  • 1,069
6 votes
2 answers
755 views

How does molecular structure contribute in the property of fluorescence?

Fluorescence is the property which is exhibited when electrons emit wavelength of light lower than the one they absorbed so does that mean we can make every molecule to become fluorescent? I wanted to ...
0 votes
0 answers
62 views

Why Lambert's law does not hold for photoresistors?

Why don't photoresistors made of Si obey Lambert's cosine law? Is it related to the dark current of the photoresistor? I couldn't find any solution while searching the web.
3 votes
2 answers
110 views

A good lab demonstration of this particular optical transform pair?

At about 1:11 the video linked below shows what think is the optical Fourier transform of a sine wave as approximated by a saw blade. https://www.youtube.com/watch?v=jzmqeRp_tmk The set-up appears to ...
  • 974
2 votes
0 answers
45 views

How would I find what specific wavelength I need to measure for a specific chemical in spectrophotometry (calcium perchlorate)?

I am currently doing a research project, and for it, I would like to use a photospectrometer to find the concentration of Calcium Perchlorate in my sample solutions. My current method of data ...
3 votes
3 answers
487 views

How to Combine an Emission spectrum into a colour? [closed]

I am trying to wrap my head around the flame test, and for the most part, it is making sense. My question is their a way to figure out the colour of a flame of an unknown element given the emission ...
  • 39
6 votes
2 answers
601 views

Why does calcium emit circularly polarized light?

One page 31 of Quantum Metrology, Imaging, and Communication by Simon, Jaeger and Sergienko, the authors state that: ... calcium has two electrons in its outermost, partially filled shell; these ...
  • 169
1 vote
1 answer
77 views

example of endothermic luminescence?

Someone posed an interesting question to me the other day: is all production of light accompanied by the generation of heat? I have found that the question as posed invites vague answers, so I thought ...
1 vote
0 answers
18 views

Can polarizing film reflect light instead of blocking light?

I was thinking about how to electorally switch glass between transparent and reflective just out of curiosity. I thought that maybe you could polarize the reflective glass in the vertical direction ...
0 votes
1 answer
47 views

Fluorochrome (fluorescein) emission decay when linked to macromolecule

I measure the intensity and polarization of light emitted from a blood sample that contains excited fluorescein (experiment known as fluorescence polarization assay). The excitation is done, as usual, ...
1 vote
0 answers
69 views

What is the amount of UV light required to make fluorophores glow and what is the minimum amount of electricity needed to achieve this?

So I have heard that fluorophores glow under UV light, so I was wondering what is the minimum amount of UV light needed to make the fluorophores glow and what would be the minimum amount of ...
  • 125
7 votes
1 answer
704 views

Does all fire only emit light on its outermost shell?

This question is about light emission, which may overlap with physics, but I am most interested in combustion and types of flame (incandescence, petrochemical fuel flames, nuclear ractions). Consider ...
  • 189
-1 votes
1 answer
66 views

Does electron emit photon when it moves? [closed]

When the photoelectric effect happens or blackbody radiation happens or when an electron jumps from a ground to an excited state, we say light is emitted by electron. Now, light is made up of photons. ...
  • 190
3 votes
1 answer
63 views

Which ceramic-like material is used in halogen MR16, GU5.3 and so on bulbs?

I hope this question belongs in here; I cannot think of any other better place to ask it. Which kind of material is used in dichroic halogen bulbs to attach the bulb itself to the reflector and keep ...
  • 131
3 votes
1 answer
50 views

Photodissociated iodine laser and population inversion

Iodine molecules ($\ce{I2}$) can absorb in the visible region and dissociate into $\ce{2 I^.}$ radicals. One of the I atoms is in ground electronic state $\mathrm{^2P_{3/2}}$ and the other I atom is ...
  • 5,507
0 votes
1 answer
49 views

Relation of Energy required to change an orbit by electron of H atom with spectrum

We have the value for expression of line spectrum of hydrogen. $\Delta E = 13.6 \cdot Z^2 \cdot \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right)$ Amount of energy required by electron to change its ...
2 votes
0 answers
80 views

Excitation states of neon (or other gas) inside neon lights

I'm interested in the spectra of gas discharge tubes. Taking neon as an example, when I look up on NIST the spectra for neon, I find excitation states up to Ne IX. Where do I find/how do I work out ...
  • 21
3 votes
0 answers
92 views

How does Mars rover Curiosity's ChemCam's infrared laser produce a 100,000 K plasma plume (kT = 8.6 eV)?

Mars rover Curiosity's ChemCam uses a pulsed diode-pumped solid-state laser (DPSS) at 1064 nm to excite material on the surfaces of rocks up to 7 meters away, and a large aperture telescope to collect ...
  • 5,573
0 votes
1 answer
63 views

Actual color of colloids [closed]

I have read that the color of colloid depends upon the wavelength of light scattered by the dispersed phase and also in the sense in which the receiver receives the light. If all of this depends on ...
  • 23
1 vote
1 answer
325 views

Colour due to transmission and reflection

It makes sense to me that when looking through a sample (observer | sample | light), it should appear as the opposite of the light absorbed, but it does not make sense to me to expect the same when ...
  • 116
11 votes
1 answer
1k views

How would you know if the light emitted is of one wavelength or if it is a mixture of two or more wavelengths? [closed]

I am just learning some chemistry after a long time without studying it and I have thought about something. Some copper compounds emit green light when heated to flame. So, I would like to know if it ...
  • 241
1 vote
1 answer
398 views

Difference between flame test and ability to show photoelectric effect [closed]

My textbook says magnesium doesn't give flame test. But it also says that it is a good photoelectric material. Are both concepts using "visible" light to remove or excite electrons? What is ...
0 votes
1 answer
261 views

Turning of a paddle wheel when exposed to light

So, we observe that in the discharge tube experiment when a very light paddle wheel is placed in the path of cathode rays, it starts turning due to the particle nature of the rays. My question is if ...
  • 103
2 votes
1 answer
52 views

Predicting color of a TMB derivative affected by peroxidase

The ELISA test on HIV works by verifying the presence of peroxidase within samples. The verification process is done through the enzymatic reaction that said peroxidase has on TMB (3,3',5,5'-...
0 votes
0 answers
44 views

Working principle of Fisher-Price Light Sketcher

I was just searching around in my store room and I found this Fisher-Price Light Sketcher. I am just amazed how the light from the pen draws on the board without even contact! I searched a lot but ...
0 votes
0 answers
245 views

What effect does the dye color have on the kinetics of a commercial lightstick?

According to thoughtco: If fluorescent dyes weren't put in glow sticks, you wouldn't see any light at all. This is because the energy produced is usually invisible ultraviolet light. Fluorescent dyes ...
16 votes
2 answers
1k views

How were x-ray diffraction patterns deciphered before computers?

I know the general idea behind x-ray crystallography is to take a high quality crystal and place it in the path of an x-ray beam. Areas of high electron density will diffract the beam and lead to ...
  • 884
3 votes
1 answer
236 views

What gives rise to the color of sapphires?

Here is what I know: Sapphires are composed primarily of $\ce{Al2O3}$ (in pure form colorless) as well as Fe and Ti (trace impurities responsible for the color). I know that the proportion and ...
  • 884
0 votes
0 answers
113 views

Absorption of UV Light and what color would be seen?

I am mathematically experimenting with different wavelengths of light that a fictional material would absorb. I thought of a material that absorbs a wavelength of $\pu{193 nm}$. This wavelength ...
  • 111
8 votes
1 answer
1k views

What causes the blackening of light bulbs

in 1878, Thomas Edison (or rather William Joseph Hammer) added an anode in a light bulb in order to catch the flux of electrons coming out from the carbon filament and reduce the phenomenon of ...
  • 251
2 votes
1 answer
233 views

What molecules are produced in carbon arc lamp and how do they produce light?

I am curious about the chemistry of the arc lamp (an indirectly for the incandescent bulbs) thus I would like to ask the following. It is a common understanding that the electrons pushed inside an ...
  • 251
3 votes
2 answers
811 views

Cause of continuous spectral lines [closed]

We know different types of atoms have different spectral lines. But what exactly are the spectral lines representing? What causes white light to have a continuous spectra while other atoms show ...
28 votes
2 answers
7k views

When a candle burns, why does the top of wick glow if bottom of flame is hottest?

Totally an elementary question. Staring at a candle, it appears that the bottom of the wick is dark whereas the top glows. However the bottom of the flame (the blue) is the hottest. Is the reason ...
  • 391
2 votes
0 answers
51 views

How do we determine the proportions of hydrogen to helium (to other elements) that make up the Sun given the absorption spectra?

I am reading about the composition of the Sun and how it is made up of mostly hydrogen (~90%) and helium (>10%) and other elements with much smaller quantities. The explains that different elements ...
0 votes
0 answers
36 views

Photochromism time of colour change

I know there are chemical pigments/dyes which produce an immediate reversible colour change in UV or direct sunlight. Is there a way to postpone the colour change so that it does not happen ...
  • 1
1 vote
1 answer
351 views

How to assess sunscreen effective via blueprinting?

How do I assess the effectiveness of sunscreen creams by using the blueprinting process? I know blueprinting is done when something is sensitive to light and this may cause reactions to produce a ...
2 votes
2 answers
97 views

Directional emission from molecules

This might be a silly question (probably is). When a molecule absorbs it has a transition dipole moment, a measure of how strongly a certain transition will interact with light will depend on how ...
  • 572
0 votes
2 answers
64 views

Process of transferring kinetic energy in regard to photons. [closed]

Now I know that temperature is the average kinetic energy of atoms, molecules and compounds. Photons increase the kinetic energy/temperature of molecules since photons are pure energy. Hence, wouldn't ...
-1 votes
1 answer
165 views

How much heat is created by absorbent-type sunscreens?

I have a friend who claims her dermatologist told her than sunscreen was what was burning her skin. (I think it's much more likely that her rash/burn was either a sunburn, a skin reaction to some ...
5 votes
1 answer
812 views

Why objects usually don't exibit fluorescence/phosphorescence?

We learn in school that the color we perceive is determined by the light that is reflected back at us. Not all wavelengths of light reflect back at our eyes, some wavelengths are absorbed. I'm ...
  • 1,608
4 votes
2 answers
371 views

Will borosilicate glass absorb 808nm laser light?

Will borosilicate glass absorb 808nm laser light? If it instead refracts, then what is the refractive index? Also, will borosilicate reflect lower frequencies of light like those used in non contact ...
user avatar