Exploring electromagnetic energy

energy from the Sun travels through space to the Earth what form of energy can travel through space can this same kind of energy be generated and used by man [Music] [Music] energy like that of the sun can be generated on Earth here's one way to do it we connect a battery to a switch a current meter and a coil of wire when we turn the switch on a steady electric current flows a compass shows us that a steady Electric current is surrounded by a magnetic field steady current steady field now suppose the current is made to pulse on and off a pulsing current produces a pulsing field now the field moves through space and can be detected at a second coil over here [Music] [Music] electro magnetic energy moving through [Music] space here the field ising about one time each [Music] second we can make more four pulses per second with a vacuum [Music] tube at several thousand pulses per second the electromagnetic energy is called radio [Music] waves as the frequency of the pulses increases we know the energy by different names [Music] the family of electromagnetic energy waves is called the electromagnetic spectrum all are electromagnetic energy waves pulsing at different frequencies [Music] let's see how we use each group electromagnetic energy traveling through space is the basis of radio [Music] broadcasting but there are many radio transmitters [Music] [Music] how can these radio waves be separated each station transmits a different number of pulses per [Music] second the number of pul per second is called the [Music] frequency your radio only one frequency through at a [Music] time at 600 kilocycles on your dial for example your radio receives electromagnetic energy at a frequency of 600,000 pulses per second higher frequencies are used to transmit pictures still higher frequencies called microwaves are generated for radar [Applause] at these frequencies electromagnetic waves will bounce from some objects [Applause] [Music] at slightly higher frequencies electromagnetic energy makes us feel warm any source of heat radiates infrared we use these frequencies every day higher frequency stimulate the nerves in your eyes electromagnetic energy we call different frequencies appear to us as different [Music] colors but our eyes detect only a small number of the frequencies that make up the entire electromagnetic Spectrum like all electromagnetic energy light is a pulsing electromagnetic field a photoelectric cell can measure the energy of light [Music] in nature the energy of light makes possible the growth of plants that give us [Music] food at slightly higher frequencies electromagnetic energy is called ultraviolet it's invisible to our eyes but we see its work as it Tans our [Music] skin the energy from an UltraViolet lamp will cause the minerals in certain rocks to Glow the minerals absorb the ultraviolet and radiate it back at at lower frequencies including visible light this is called fluorescence this principle is used in a fluorescent light inside the tube is a special coating a source of ultraviolet energy causes this coating to flues slightly higher frequencies called x-rays are generated by a special tube x-rays pass through less dense objects leaving shadow pictures of dense objects some of the highest frequencies we know are released when an atom nucleus splits apart a splitting atom releases particles and electromagnetic energy called gamma rays uranium ore releases gamma rays which can be detected by a Gyer [Applause] [Music] [Applause] counter so we have that electromagnetic energy is known by different names according to its frequency but all electromagnetic energy is a pulsing electromagnetic field traveling through space we've seen that the frequency the number of waves per second is the only difference among these [Music] groups we use electromagnetic energy to communicate to warm our homes to see to keep healthy to learn about the [Music] world we know that every Star including our sun radiates electromagnetic [Music] energy but are there frequencies beyond the ends of the known Spectrum [Music] we have only begun to understand and use this energy that travels through space [Music] [Music] what [Music]