WHAT '' REPORT 'PHOTONS.
Light is a valuable source of information. On its intensity, spectrum, distribution in space, change over time can be seen on many phenomena occurring in nature. Not for nothing for people from all the senses is the main sight. But the possibility of limited. Limited range of light waves which the eye can see, the person is not able to quantify the amount of luminous flux.
It is not always in the registration plate light can help. For example, you cannot use it to fix changes in light intensity over time. In addition, the photographic plate must be more to process, but this is not always convenient and affordable.
And here comes to the aid of electronics. An indispensable instrument for recording weak light fluxes is photomultiplier. Based on the repeated used effect of secondary electron emission, like "multiplication" of electrons, this device has a very high gain (up to several million times) and allows you to register even single photons.
In addition to a very high sensitivity photomultiplier tube has a number of advantages. Practically it is inertia, that is, it can be registered very rapid changes in flux. The spectral characteristics of the photomultiplier photocathode and by the type of material, from which you are part of the light-carrying balloon. It may be, in particular, is made in such a way that will have high sensitivity in the ultraviolet region, i.e. where the human eye does not sense light.
Sometimes it is necessary to measure ultraviolet radiation in daylight, and do not want daylight working on a photomultiplier. For this purpose, use so-called "blind" multipliers, almost insensitive to daylight, but having a sufficiently high sensitivity in the region of shorter light waves.
The question may arise - how does photomultiplier to biology?
It turns out that the most direct. Just as astronomers, studying the spectrum and other parameters of the light that came to us from distant stars, unraveling their mysteries (determine the composition and surface temperature), biologists, recording the light coming from a variety of biological objects - cells, tissues and whole organisms Make important conclusions about the properties of living matter and the phenomena occurring in it.