what are the differences between normal incandescent blue glass lamp and blue LED and blue LASER ?
Basically, the difference is in the spectrum amplitude.
Of course incandescent bulbs, led and laser are very different also in actual delivered radiation and energy consumption.
From the point of view "of the target" however, an incandescent bulb emits a black body spectrum with a lot of energy in the infrared range. The blue glass has the only effect to screen a certain amount of visible energy in the range of yellow and red, with poor effect on infrared, i.e. in irradiation of heat. Opposite, a blue laser delivers light with a definite wavelength with a band width even lower than 1 nm. An incoherent blue led delivers a narrow band spectrum as well, again with no infrared emission, but a band width of several nm . It is also worth to be noticed that usually laser sources are designed do produce highly collimated beams while bulbs and led can more easily illuminate wide targets.
Thanks Mr. Frigerio for your helpful answer.
as a biologist I am not so familiar with physical properties of light, I would like to ask you if incandescent blue lamp (blue glass) emit in the blue region of the electromagnetic spectrum or it is a normal white lamp with blue glass that has some effect allowing the emission of the blue light (up to 400 nm)?
what do you mean by "the blue glass has the only effect to screen a certain amount of visible energy in the range of yellow and red" ?
You should look at the manufacturer's information for a specific brand of lamp to see how it works, but if the glass is described as blue, then that probably means it preferentially transmits the blue light from a normal incandescent light filament. The filament emits visible light over most or all of the visible spectrum, as well as infra-red radiation, when it is heated by running a current through it.
A blue light-emitting diode will produce a much narrower spectrum centered within the blue region of the visible spectrum (i.e. probably with some green and violet light as well, with the overall appearance being blue). A blue laser will produce only blue light of one wavelength/frequency value.
Keith Fraser's explanation is correct, however consider that green and violet emission from blue leds are, for most of the uses, negligible. In fact in commercial white led lamps, a blue led is coated with a fluorescent medium in order to produce green and red light thus obtaining a more or less white emission.
If you want to irradiate biological cultures with a blue light source, discard incandescent bulbs and even halogen lamps since they produce anyway an higher amount in IR range than in visible.
Valuable blue light sources are metallic halide lamps, also known as daylight sources. They are used in outdoor illumination and generate light by a discharge in a suitable gas mixture. Remember that they have also a certain UV emission (< 400 nm) which could even be of safety concern at close range.
The blue incandescent bulb is emits the light through spontaneous emission that is light photons emits in all the directions also the photon will not maintain constant phase and requires high voltage about 230v for its working.
The led is the semiconducting material this also emits light through spontaneous emission, will not maintain constant phase difference and requires less voltage for its working (5v)
The laser is only the source which emits light through stimulated emission, will maintain constant phase difference and have directionality and high intensity also it requires power depending on type of laser .
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