Incandescence
Light emitted from a material because of high temperature
Electric discharge
When an object emits light from heated gas, or vapour, instead of a heated wire
Fluorescence
Light that is emitted during exposure of the source to ultraviolet light
How does a fluorescent bulb work?
- When the electrodes are charged, they emit electrons.
- The electrons travel through the gas, releasing mercury as they collide with mercury atoms.
- The exited mercury emits UV light, which the phosphor gas absorbs to emit visible light
What are the uses of fluorescence?
- For forensic scientists to find blood, urine, and semen (all fluorescent) in a crime scene
- Used by dentists and hygienists to identify unhealthy oral tissue
- Used in many documents, such as money, legal documents, admission tickets, etc.
- Some theatre performers use paint with fluorescent dyes, so when the theatre is dark and only UV light is shining on the performers, the audience can see the fluorescent light coming from the paint
Luminescence
Light that is generated without heating the object
Phosphorescence
Similar to fluorescence, except the exited atoms retain energy for much longer, which means the light will last longer
What are the types of luminescence?
Fluorescence, phosphorescence, chemiluminescence, and bioluminescence
Chemiluminescence
Light that is produced through chemical reactions without a rise in temperature
Bioluminescence
A type of chemiluminescence. Light that is produced by biochemical reactions in a living organism’s living cells
Wavelength
The distance from one crest (or trough) to the next
Electromagnetic spectrum
- A diagram that shows the range, or spectrum, of electromagnetic waves in order of wavelength or frequency
- The color red has the longest wavelength, while the color violet has the shortest wavelength
