Radio Radio waveswaves

MicrowaveMicrowaves/Radars/Radar

Infrared Infrared WavesWaves

This is Junction Hill News, with a question from

Anita Know

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?'

"

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.

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.

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.

This is what This is what we seewe see

This what a bee sees

A bee’s perception is

different from ours

Anita, thanks for your question. This has been another installment of

Junction Hill News. Good Day

It might seem strange to you to call something you It might seem strange to you to call something you can’t see light, because the light you are most familiar can’t see light, because the light you are most familiar with is visible light.with is visible light.

In this section we will learn about many other types of In this section we will learn about many other types of electromagnetic waves, including X rays, radio waves, electromagnetic waves, including X rays, radio waves, and microwavesand microwaves.

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?

• The entire range of electromagnetic waves is called the The entire range of electromagnetic waves is called the electromagnetic spectrumelectromagnetic spectrum

• Categories of waves in the electromagnetic spectrum Categories of waves in the electromagnetic spectrum include radio waves, microwaves, and visible lightinclude radio waves, microwaves, and visible light

• Radio waves have the longest Radio waves have the longest wavelengths in the wavelengths in the electromagnetic spectrum. electromagnetic spectrum. These waves can be longer These waves can be longer than a football field or as than a football field or as short as a football. short as a football.

• Radio waves do more than Radio waves do more than just bring music to your radio. just bring music to your radio. They also carry signals for They also carry signals for your television and cellular your television and cellular phones.phones.

Radio waves cover a wide range of Radio waves cover a wide range of waves in the electromagnetic waves.waves in the electromagnetic waves.

Radio waves are low energy wavesRadio waves are low energy waves They carry enough energy, however, They carry enough energy, however,

to be used for broadcasting radio to be used for broadcasting radio signalssignals

Radio stations encode Radio stations encode sound information sound information into radio waves by into radio waves by varying either the varying either the waves amplitude or waves amplitude or their frequency.their frequency. Changing amplitude or frequency is Changing amplitude or frequency is

called called modulationmodulation

Live on 107.1 FM

Dad, what does FM

stand for?

Well son, FM stands for frequency

modulation

• AM radio waves have longer wavelengths than FM radio AM radio waves have longer wavelengths than FM radio waveswaves

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

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

Radio waves travel at 186,000 miles per second through air. In contrast, 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. 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 If a modulation is made of the radio wave that exactly reproduces the amplitude and frequency characteristics of the original sound wave, amplitude and frequency characteristics of the original sound wave, then sound can be transmitted rapidly over long distances. then sound can be transmitted rapidly over long distances.

This leads to a very interesting phenomena. During a live broadcast in 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 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 second before it can be heard by the New York audience sitting in the back of the concert hall.back of the concert hall.

Television signals are also carried by radio Television signals are also carried by radio waves. waves.

Most television stations broadcast Most television stations broadcast radio waves that have shorter radio waves that have shorter wavelengths and higher frequencies wavelengths and higher frequencies than those broadcast by radio than those broadcast by radio stations.stations. Television signals are still Television signals are still broadcast using amplitudebroadcast using amplitude modulation and frequencymodulation and frequency modulationmodulation Television stations use frequency-modulation for Television stations use frequency-modulation for

sound and amplitude-modulation for pictures.sound and amplitude-modulation for pictures.

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

How does cable TV

work

Microwaves have shorter wavelengths Microwaves have shorter wavelengths and higher frequencies than radio waves.and higher frequencies than radio waves.

Microwaves carry more energy than Microwaves carry more energy than radio waves.radio waves.

That’s neat dude, but how does my

microwave work??

• 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.

Microwaves are also Microwaves are also used in radarused in radar

Police officers use Police officers use radar to determine radar to determine the speed of a carthe speed of a car

Radar is also used to Radar is also used to monitor the monitor the movement of movement of airplanes and to airplanes and to help ship captains help ship captains navigate at night or navigate at night or in foggy weatherin foggy weather

• 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.

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

                          

    

• 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.

                          

    

Radar can be used for landform imagery

Mammoth, California

Infrared light lies between the visible and microwave Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. portions of the electromagnetic spectrum.

Infrared light has a range of wavelengths, just like visible Infrared light has a range of wavelengths, just like visible light has wavelengths that range from red light to violet. light has wavelengths that range from red light to violet. "Near infrared" light is closest in wavelength to visible "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. of the electromagnetic spectrum.

The longer, far infrared wavelengths are about the size of The longer, far infrared wavelengths are about the size of a pin head and the shorter, near infrared ones are a pin head and the shorter, near infrared ones are microscopic.microscopic.

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.

This heat is about the

kill me

Speak for yourself

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

                                                        

         

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.

                                                                

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

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.

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.

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