Physics: Electromagnetism At Work

events of the past and present shape tomorrow our Vital concern is you today's youth for our future depends on you to untangle today's problems we need to understand yesterday we hope this film series will make you aware of the people places and events which have help shape our nation and our world manufacturers Handover is pleased to sponsor this Ed educational film as a special service to schools in the New York City area [Music] [Music] 300 years ago the great scientist Sir Isaac Newton proposed that various colors of light were basically similar phenomena about a century ago another great English scientist James Clerk Maxwell suggested that all possible forms of electromagnetic energy from radio waves to light waves to the later discovered Atomic radiation were similar wave phenomena this program describes the various forms of electromagnetic energy and how they have been applied to meet human [Music] needs like ocean waves long rolling swells or short breakers on a beach some light and other energy Transmissions are basically wav likee in character the various types of energy Transmissions light radio waves and others differ only in wav lengths together making up the electromagnetic spectrum a Pioneer in understanding radiant energy was Dutch born physicist vilhelm Renkin in 1895 experimenting with electrical discharges in a blacked out vacuum tube he noticed that some distance away a sheet of paper treated with barium Platinum cyanide began to emit light he had discovered invisible Rays capable of penetrating solid objects and exposing photographic plates he called his unknown Rays X-rays and his first x-ray photographs amazed the medical and scientific World a year later arri Beckel who had been investigating rin's x-rays discovered that mineral crusts placed on photographic plates wrapped in light tight black paper would make an image on the plates without being exposed to [Music] light radiations from the minerals penetrated the black paper and in later experiments penetrated thin strips of aluminum and copper beel had discovered radioactivity though he didn't call it by that name [Music] in 1898 Marie C using instruments devised by her husband Pierre began to examine all the elements then known for traces of radiation finding many spontaneous sources she proposed the word radioactivity to describe the phenomenon later she succeeded in isolating a new strangely radioactive element from an ore of uranium she called it radium [Music] also in 1898 a New Zealander Ernest Rutherford concluded a lengthy study that led to the realization that there were two types of radiation each with different powers of penetration he called them Alpha and beta an even more penetrating type of radiation was discovered by PV vard it was somewhat similar to rin's X-rays and given the name gamma electromagnetic radiation such as gamma rays and x-rays is invisible and Silent we measure such radiation by its [Music] wavelength in this diagram we can see types of radiation with three distinct [Music] wavelengths this is a rela ly long wavelength we can create these waves with special equipment which transmits them from a broadcasting station the waves can measure up to a kilometer from Crest to Crest we cannot see or hear the waves but a radio receiver can transform them into sound waves we can here the waves will pass through buildings and people and Do no harm they do however lose some of their strength as they pass through things the concrete and steel reinforcing rods in an overpass absorb so much radio energy that there is none for the radio to pick up shorter wavelengths can be used in transmitting TV pictures the length of the rods on TV antennas is related to the wavelengths of transmission radar employs shorter waves wavelengths which will not pass through aircraft or ships instead radar waves bounce off objects returned to the cender as images on a [Music] screen shorten the wavelengths a little further and we have microwaves today people use microwaves for cooking microwaves can be dangerous but safety devices are built into microwave [Music] ovens let's see how far we've moved down the electromagnetic spectrum so far we have seen radiations from Radio TV radar and microwaves now let's discuss an even shorter wavelength infrared radiation such infrared rays are used to operate a TV by remote [Music] control we can detect infrared with our bodies and feel the Deep penetrating wavelengths they bring relief to sufferers of muscular pain we also feel infrared coming from fires and stoves [Music] by using special heat detecting film we can take pictures of heat like this rescue workers find people buried under debris by using heat detecting cameras so far none of the radiations discussed have been visible to our eyes to detect them all you have to use special instruments now we'll consider wave lengths which are even shorter the visible light wavelengths from 400 to 700 M or 4,000 to 7,000 angstroms each color you detect with your eyes has a particular wavelength as the wavelengths shorten they reach the level of ultraviolet light such ultraviolet light promotes tanning though Too much exposure can be harmful [Music] ultraviolet light has other uses here forensic scientists use ultraviolet light to detect alterations and forgeries in documents the document on the right is genuine the left one is false as wavelengths become shorter still we reach x-rays since they were discovered by renken a century ago x-rays have proved very very [Music] useful we use the radiation we call x-rays to penetrate solid objects and produce images for doctors to examine we are now down to very short wavelengths less than the thickness of an atom we need to know about atoms because that that's where the x-rays start from inside atoms an atom is small indeed for instance It's probably hard to believe but there are more atoms in a pencil dot than there are people in the [Music] world yet atoms are very important because everything not just the pencil dot but everything is made up of atoms you are I am rocks liquids all consist of atoms let's look at a typical atom each atom is something like a miniature solar system the outer shell consists of tiny particles these are electrons The Cloud of electrons surrounds a central part called the nucleus the nucleus is made of two kinds of particles which are relatively much bigger than electrons but let's return to x-rays because they have energy they could do harm if not carefully controlled the source of the x-rays is surrounded by lead so that the operator and patient are protected only a limited amount of the x-rays are used to make a picture [Music] x-rays are energy coming from the innermost orbits of electrons of course only certain atoms give out x-rays gamma rays are similar to x-rays but have more energy here they are in their place in the electromagnetic spectrum gamma rays are potentially hazardous to life but we can protect ourselves from their Effects by ensuring there is a safe distance from them or by shielding the source with very thick lead or concrete like x-rays they can be used in medicine carefully controlled gamma rays can be directed to kill cells which have become tumors many years ago hypodermic syringes were expensive so each syringe was used on many patients each time they were immersed in boiling water water to kill off any germs which might cause infection nowadays syringes are sterilized by gamma radiation while in a new germ proof bag each syringe much cheaper than in the past is used once then thrown away boxes of syringes traveling on a conveyor belt move through a specially shielded room containing a radioactive piece of cobalt metal the gamma don't make the boxes on the conveyor system or the syringes radioactive but they do kill any germs on the syringe radiation plants like this run 24 hours a day 7 days a week processing surgical devices cosmetic powders and Plastics even food can have its storage life extended by gamma [Music] radiation here's another use for gamma Rays testing the combustion chambers of jet engines they run for hundreds of hours at very high temperatures and it's essential that no cracks develop in the metal if there are fine cracks they may not be detected by the human eye so once again gamma rays are used to take pictures if defects exist the chambers are replaced as this program has shown most forms of r radiant energy are both useful and potentially hazardous sunlight for example is necessary to life in many ways without it we'd have no food yet the sun's Rays can harm us even kill us as with sunlight so with most wavelengths of the electromagnetic spectrum once we've learned how to deal with them safely to protect ourselves they've proven very useful [Music] the science screen report has been presented to you as a community service of Manufacturers Handover