Stupid question about fluoresence

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In summary, if a phosphor such as ruby (Cr:Al2O3) is excited with a light source near its main pump band (~556nm), it will emit light with a different color than the source light. For instance, shining a green light onto a piece of ruby will make it appear red. However, it is unclear if the light source needs to be removed in order to see the shifted emitted light. This is a commonly asked question and a sanity check is needed to confirm. Within a laser cavity, the pump light is always on and the endmirrors filter the laser light spectrally. This can be seen in the setup of diode-pumped Nd:YAGS.
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If you have a phosphor such as ruby (Cr:Al2O3) and you excite it with a light source near its main pump band (~556nm) then you should see emit light with a difference in color from the source light, correct? For example if I shined a green light onto this piece a ruby, it should appear red should it not? Or, does the light source need to be removed in order to see the shifted emitted light? I know this is probably a stupid question but I really need a sanity check right now.
 
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Within a laser cavity, the pump light is always on; the endmirrors take care of spectrally filtering the laser light. Look at how diode-pumped Nd:YAGS are set up, for example.
 
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Your question is not stupid at all! In fact, it shows that you have a good understanding of fluorescence. Yes, if you excite a phosphor such as ruby with a light source near its main pump band, you should see emitted light with a different color from the source light. In the example you gave, if you shine a green light onto the ruby, it should appear red because the ruby will absorb the green light and emit red light. However, to see the full effect of the fluorescence, it is best to remove the light source so that the emitted light is not competing with the source light. This will allow you to see the full intensity and color of the fluorescence. So, in summary, your understanding is correct and there is no need for a sanity check. Keep asking questions and learning!
 

1. What is fluorescence?

Fluorescence is a phenomenon where certain substances absorb light at specific wavelengths and then emit light of a longer wavelength. This results in the substance appearing to glow or emit light.

2. How does fluorescence occur?

Fluorescence occurs when a substance, known as a fluorophore, absorbs light at a specific wavelength and then quickly releases that energy in the form of light at a longer wavelength. This process is known as fluorescence emission.

3. What causes certain substances to fluoresce?

The ability of a substance to fluoresce depends on its molecular structure and the presence of certain atoms or molecules that can absorb and emit light. This property is known as fluorescence quantum yield.

4. How is fluorescence used in science?

Fluorescence is used extensively in scientific research and various applications. It is commonly used in microscopy, flow cytometry, and medical imaging techniques like fluorescence spectroscopy and fluorescence in situ hybridization (FISH). It is also used in environmental monitoring and industrial processes.

5. Is fluorescence harmful?

In most cases, fluorescence is not harmful. However, some fluorescent substances, such as certain dyes or chemicals, can be toxic. It is important to follow safety precautions when working with fluorescent materials and dispose of them properly.

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