Seeing the Invisible.

Kaipara and Waitemata Echo, 10 April 1914, Page 8

Seeing the Invisible.

WEIRD SENSE OF SCIENCE. It will come as news to most people that science has invented instruments that go two degrees beyond the most powerful microscope in detecting small objects. The first of these is known as the ultraviolet microscope. This takes advantage 'of the fact that a photographic plate can often see things that the human eye cannot, and for the following reason : Things cannot reflect light, and consequently cannot be seen, that are smaller than the smallest wave length of light that falls on them. Violet light is the smallest that can be possibly seen with the human ,- eye. . Hut there exists a much ;«. smaller wuve length in the part of the spectrum not visible to the eye, '. ;,<* called, the ultra-violet light. This w l^ has the peculiar property of affeet*X& V>Mng a photographic plate just as any p4y ~ ■ ■

otfier light would, so that we get I a true picture of the minute object ! that is under examination. | Thus the deficiency of the eye is" j made up for by a mechanical inven- ! tion of the human brain. This ul- ' tra-violet light, though not detect- ' able by the human eye, is easily seen by small animals and insects. J It has been tried with great sue- ' cess on ants especially. With this ultraviolet microscope the smallest ; objects that can be photographed .' with definiteness of dimensions are j brought out with wonderful dis- i tinctness. j 1 But there is one other instrument i that can detect much smaller oh- ; jects, though their shape or size j cannot be seen, and that.is known! as the ultra microscope. This takes j . advantage of the fact that a small j i object will scatter any light that j falls on it. To make the meaning ' | clear, all of us have noticed a beam | |of light entering a room full of | : floating dust particles. We see only \ the dust particles in the beam of light. The reason we see them is | because each little particle scatters the light that falls on it in all di- ' | reclions, and some of the scattered ! light enters the eye. j This is the principle on which the ; ultramicroscope is based. Light is made to fall on the object in such ■ a way that none of the direct light I can enter the eye. Then the particles appear as small points of light. In this way it has been proved that j the colouring 'in red glass is not diffused, but consists of thousands of little red particles close together.