Electromagnetic Spectrum

1. Electromagnetic Spectrum Microwaves/Radar Radio waves Infrared Waves

2. Junction Hill News She writes, “one afternoon, I was outside watching a large bumblebee hovering over a bright yellow rose. I wondered, 'Can bees see colors we can't?' " This is Junction Hill News, with a question from Anita Know

3. Junction Hill News Anita, what we see as sunlight reflects from objects -- and all visible light is part of a larger spectrum of energy. Bees can see ultraviolet -- a color humans can only imagine -- at the short-wavelength end of the spectrum. But, unlike humans, bees can't see red -- at the longer wavelength end of the spectrum. Red looks black to bees.

5. Many flowers have ultraviolet patterns on their petals. Bees can see these patterns. They use them as visual guides -- like a map painted on the flower -- directing them to the flower's store of nectar. Some flowers that appear non-descript to us have strong ultraviolet patterns.

6. Bees' eyes are different from our eyes in other ways as well. For example, honeybees can perceive movements that are separated by 1/300th of a second -- so that if a bee flew into a theater, it could differentiate each individual movie frame being projected.

7. This is what we see A bee’s perception is different from ours This what a bee sees

8. Junction Hill News Anita, thanks for your question. This has been another installment of Junction Hill News. Good Day

9. It might seem strange to you to call something you can’t see light, because the light you are most familiar with is visible light. In this section we will learn about many other types of electromagnetic waves, including X rays, radio waves, and microwaves.

10. Remember, even though there are many types of electromagnetic waves, each type of wave travels at the same speed. The speed of a wave is determined by multiplying its wavelength by its frequency. So, electromagnetic waves having different wavelengths can travel at the same speed as long as their frequencies are also different. What does that mean?

11. The entire range of electromagnetic waves is called the electromagnetic spectrum • Categories of waves in the electromagnetic spectrum include radio waves, microwaves, and visible light

12. Radio waves have the longest wavelengths in the electromagnetic spectrum. These waves can be longer than a football field or as short as a football. • Radio waves do more than just bring music to your radio. They also carry signals for your television and cellular phones.

13. Radio waves cover a wide range of waves in the electromagnetic waves. Radio waves are low energy waves They carry enough energy, however, to be used for broadcasting radio signals Radio stations encode sound information into radio waves by varying either the waves amplitude or their frequency. Changing amplitude or frequency is called modulation

14. Well son, FM stands for frequency modulation Dad, what does FM stand for? Live on 107.1 FM

15. AM radio waves have longer wavelengths than FM radio waves • AM radio waves can travel farther than FM waves because they can reflect off the ionosphere, FM cannot.

16. Most radio stations that broadcast mostly music use FM waves. That’s because more information can be encoded by using frequency modulation than by using amplitude modulation Because FM waves carry more information, music broadcast from FM stations sounds better

17. Radio waves travel at 186,000 miles per second through air. In contrast, sound waves travel at only 1/5 of a mile per second. If a modulation is made of the radio wave that exactly reproduces the amplitude and frequency characteristics of the original sound wave, then sound can be transmitted rapidly over long distances. This leads to a very interesting phenomena. During a live broadcast in New York, the music will reach listeners in California a fraction of a second before it can be heard by the New York audience sitting in the back of the concert hall.

18. Television signals are also carried by radio waves. Most television stations broadcast radio waves that have shorter wavelengths and higher frequencies than those broadcast by radio stations. Television signals are still broadcast using amplitude modulation and frequency modulation Television stations use frequency-modulation for sound and amplitude-modulation for pictures.

19. How does cable TV work TV signals are transmitted to satellites around the Earth. The waves are amplified and relayed back to ground antennae and then travel through cables to your TV

20. Microwaves Microwaves have shorter wavelengths and higher frequencies than radio waves. Microwaves carry more energy than radio waves. That’s neat dude, but how does my microwave work??

21. A device called a magnetron inside the microwave produces waves by accelerating charged particles • The microwaves reflect off a metal fan at the top and are directed into the cooking chamber • Microwaves penetrate several centimeters into the food • The energy of the microwaves causes water molecules inside the food to vibrate. The vibration of the water molecules causes the temperature of the food to increase.

22. Radar Microwaves are also used in radar Police officers use radar to determine the speed of a car Radar is also used to monitor the movement of airplanes and to help ship captains navigate at night or in foggy weather

23. The satellite making this image sends out wavelengths about 5.7 cm long (C-band). This shows sea ice breaking off the shores of Alaska.

24. This satellite uses wavelengths about 20 cm in length (L-band). This is an image of the Amazon River in Brazil.

25. This is a radar image acquired from the Space Shuttle. It also used a wavelength in the L-band of the microwave spectrum. Here we see a computer enhanced radar image of some mountains on the edge of Salt Lake City, Utah.

26. Radar can be used for landform imagery

27. Mammoth, California

30. The Infrared Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. Infrared light has a range of wavelengths, just like visible light has wavelengths that range from red light to violet. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. The longer, far infrared wavelengths are about the size of a pin head and the shorter, near infrared ones are microscopic.

31. This heat is about the kill me Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat! The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared. Speak for yourself

32. Besides the sun, other objects emit infrared waves including stars, planets, buildings, trees, and you!! The amount of infrared radiation emitted by an object varies depending on the object’s temperature. Warmer objects give off more infrared radiation than cooler objects

33. Shorter, near infrared waves are not hot at all - in fact you cannot even feel them. These shorter wavelengths are the ones used by your TV's remote control.

34. Humans may not be able to see infrared light, but did you know that snakes in the pit viper family, like rattlesnakes, have sensory "pits", which are used to image infrared light? This allows the snake to detect warm blooded animals, even in dark burrows!

35. This image of a building with a tree and grass shows how chlorophyll in plants reflect near infrared waves along with visible light waves. Even though we can't see the infrared waves, they are always there. The visible light waves drawn on this picture are green, and the infrared ones are pale red.

36. This image was taken with special film that can detect invisible infrared waves. This is a false-color image, just like the one of the cat. False-color infrared images of the Earth frequently use a color scheme where infrared light is mapped to the visible color of red. This means that everything in this image that appears red is giving off or reflecting infrared light. This makes vegetation like grass and trees appear to be red.

37. This image shows the infrared data (appearing as red) composted with visible light data at the blue and green wavelengths. If near infrared is reflected off of healthy vegetation, what do you think the red square shaped areas are in the lower left of the image?