Electromagnetic Spectrum Flashcards
Radiation Fundamentals
- The fundamental unit of radiation(energy that is emitted by the sun) is the photon/light
- Photons are released from objects when matter:
- is excited thermally
- is engaged in nuclear processes (fusion, fission)
- Photons are also absorbed and reflected by matter
- The speed of photons in a vacuum (c) is 3.0 x 108 m/s but have different energies related to their wavelength
the sun
- 109 times bigger than the Earth
(diameter). - 99.86% of the total mass of the Solar
System. - Surface temperature: 5,800 K
- Energy comes from nuclear fusion of
hydrogen into helium - Emits light in virtually every part of
the EMS
Radiation Fundamentals
We relate frequency and wavelength by:
C = lembda x V
- c = speed of light **(a constant), **
- lambda = wavelength
- v = frequency.
So, we see that as wavelength increases (gets longer), the lower
the frequency (and energy). and vice versa
so frequency
is how many many waves there are in a wave lenght
- lower frequency = less waves= lower amount of energy associated
- high frequency = more waves=high amount of energy associated
EMR Spectrum
- Wavelengths range in size from radio waves which are several meters long, to visible light which is measured in microns or millionths of a meter (10-6 m)
**radio waves: **lenghier waves=less frequecy= less energy
Gamma ray: shorter wave = more frequency =more energy
Radio Waves
- Radio waves have the longest wavelengths in the spectrum
- They range from the length of a football field to larger than our planet
- You can tune a radio to a specific radio amplitude (AM) or frequency (FM)
- And listen to your favorite music
- The radio “receives” these electromagnetic radio
waves and converts them to mechanical vibrations in
the speaker to create sound
Radio Waves and space
- Astronomical objects often produce radio waves
o Thus radio telescopes can view planets, stars, and
galaxies - Since radio waves are longer than optical waves,
radio telescopes must be physically very large - In order to make a clearer, or higher resolution, radio image, radio astronomers often combine
several smaller telescopes, or receiving dishes,into an array
Microwaves
- Microwaves are the portion of waves in the spectrum at the end of the radio spectrum(next to radio waves)
- Most communication satellites use C-, X-and Ku-bands to send signals to a ground station
- Remote sensing using X, C, L and P
- Microwaves that can see through haze, light rain and snow, clouds, and smoke are beneficial for satellite
communication and studying the Earth from space
Infra-Red Waves
- The infrared region is divided into:
- Near
- Mid- (or Short wave)
▪ Near and mid are classified as reflective infrared
- Far-infrared
- classified as longwave emitted infrared
▪ These wavelengths are best for studying the longwave
thermal energy radiating from our planet
Infra-Red Waves and Heat
- Objects emit radiation as they heat up
* The thermal (or far/longwave) infrared radiation that is emitted as an object warms is what we sense as heat
o Some objects are so hot they also emit visible light—such as
a fire
o Other objects, such as humans, are not as hot and only emit
infrared waves
o Our eyes cannot see these infrared waves but instruments
that can sense infrared energy—such as night-vision goggles
or infrared cameras–allow us to “see” the infrared waves emitting from warm objects such as humans and animals
Near Infra-Red Waves
- A portion of radiation just beyond the visible spectrum is referred to as near-infrared
- This is not heat
- It is reflected, transmitted, and absorbed light and it is very useful for observing health of vegetation and soil composition
- Reflected near-infrared radiation can be sensed by satellites, allowing scientists to study vegetation from space
Visible Waves
- All electromagnetic radiation is light, **BUT **the portion of this radiation our eyes can see is called visible light
- The wavelengths of visible light fall out like a rainbow
- Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers
- Green is in the middle
- Each color in a rainbow corresponds to a different wavelength of electromagnetic spectrum
UltraViolet Waves
- Ultraviolet (UV) light has shorter wavelengths than visible light
- Although UV waves are invisible to the human eye,** some insects, such as bumblebees, can see them**
- The Sun is a source of all UV light
o **UV-C rays are the most harmful **and are almost completely **absorbed by our atmosphere
**
o UV-B rays are the harmful rays that cause sunburn
-
Only a small amount of UV-A waves hit the Earths surface and those are the ones** we use in Earth
observation Ultraviolet Imaging Spectrograph (UVIS)** used to capture imagery of Saturn’s rings (Source: NASA)
X-Ray Waves
*** X-rays **have much **higher energy **and much shorter wavelengths than ultraviolet light
- As a result we often refer to X-rays in energy rather than their wavelength
- Different objects absorb different amounts of x-rays
- Different hot bodies like the Sun and stars all emit x-rays
- We DON’T use X-rays to observe changes on the Earth
Gamma Waves
- Gamma rays have the **smallest wavelengths **and the most energy
- They are produced by the hottest and most energetic objects in the universe, such as neutron stars and pulsars, supernova
explosions, and regions around black holes -
On Earth, gamma waves are generated by nuclear explosions,
lightning, and radioactive decay - Unlike optical light and x-rays, gamma rays cannot be captured
and reflected by mirrors
o Gamma-ray wavelengths are so short that they can pass through the
space within the atoms of a detector -
Gamma-ray detectors are usually densely packed crystal blocks
o As gamma rays pass through, they collide with electrons in the crystal
o These collisions create charged particles that can be detected by the
sensor
we dont use them for earth observation
