IMAGES FROM SPACE Unit 4, Lesson 1 Pages 188-199 Electromagnetic Radiation Energy traveling as electromagnetic waves (from the sun). • Wavelength – the distance between two adjacent crests or troughs of a wave – The smaller the wavelength the more energy the wave has • Frequency – measures the number of waves passing a point per second – The higher-frequency wave carries higher energy Electromagnetic Spectrum • Spectrum – continuous range of a single wavelength • Electromagnetic spectrum – Radio waves has the longest wavelength and lowest frequency • Televisions and radios use radio waves • These receivers then produce sound waves • Microwaves • Infrared – Sometimes called “heat radiation.” • Visible light radiation – You see an object when visible from the object reaches your eyes. Ultrviolet • Ultraviolet – Wavelength shorter and contains more energy – Frequency higher – Energy powerful enough to kill living cells • X-rays and Gamma Rays – Shortest wavelengths – Highest frequency – Contain very high energy – Can also kill living cells Characteristics of Electromagnetic Radiation • Electromagnetic waves can be generated by cell phones, microwave ovens and flashlights • They are also generated by heat – Very cool materials radiate or emits energy mostly radio waves – Warmer objects may radiate mainly in the infrared – To emit visible light, object must be hot. • Light bulbs • Microwave oven –Microwaves penetrate a small distance into many materials where they are absorbed –Energy is released as heat • Ultraviolet –Can cause materials to fluoresce or glow • Documents can be protected against counterfeiting if they use symbols that can be detected by special lamps • X-rays –Pass through flesh easily by less easily through bone –Can be used to examine the insides of your body • In small amounts electromagnetic radiation can be very useful • Large amounts of any radiation can cause problems –Ultraviolet radiation – skin cancer –Gamma rays - dangerous to living organisms What Electromagnetic radiation reaches Earth? • If Earth did not have an atmosphere all electromagnetic radiation would reach Earth • Most radio and visible light radiation reach Earth’s surface. Detecting Electromagnetic Radiation • All forms of electromagnetic radiation from space can be collected by telescopes. • Special detectors must be used to form images from radiation other than visible light. – Radio waves – Detected by radio telescopes – Infrared, X-ray and Gamma ray detectors are used for those higher frequency regions. – Visible light - detected by optical telescopes Optical telescopes • Reflecting telescope – uses mirrors to collect light • Refracting telescope – uses lens to collect light • The larger the mirror or lens the more light can be collected and the fainter objects can be seen Non-Optical Telescopes • Radio telescopes – use metal mirrors to reflect radio waves onto the antennae and then to the computer to make an image. –VLA – Very Large Array in New Mexico has 26 movable radio telescopes How can people observe Earth from space? • Remote Sensing Satellites – orbit at different altitudes and directions –Low Earth orbit satellites monitor the atmosphere (a few hundred km) –Take 90 min. to orbit the Earth once • Geosynchronous - a satellite that orbits about 36,000km above the equator and it always stays above the same location as Earth rotates below it. –Most weather observations are made from satellites in this orbit. What can you learn about Earth from satellite images? They show • Evidence of human activity • How things change over time • Populated areas • Highways • Forest fires (warn people of danger) • Images of clouds and storms (hurricanes) • Auroras • Ozone variations What can you learn from space images? • Visible light can show how objects in space look. • Infrared radiation can reveal temperatures of objects. • Infrared radiation can see what is behind dust clouds. • Some very bright objects are seen better using an x-ray or gamma-ray telescopes.