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Transcript of A difficult question, thousands of years in understanding. Very difficult to study, since it cannot...
![Page 1: A difficult question, thousands of years in understanding. Very difficult to study, since it cannot be caught, and it is very difficult to measure.](https://reader031.fdocuments.in/reader031/viewer/2022020117/56649d8a5503460f94a70362/html5/thumbnails/1.jpg)
Light Waves
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The Electromagnetic Spectrum
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What is Light?
A difficult question, thousands of years in understanding.
Very difficult to study,since it cannot becaught, and it is verydifficult to measure.
![Page 4: A difficult question, thousands of years in understanding. Very difficult to study, since it cannot be caught, and it is very difficult to measure.](https://reader031.fdocuments.in/reader031/viewer/2022020117/56649d8a5503460f94a70362/html5/thumbnails/4.jpg)
What is Light?
Light is a wave that travels through the universe’s electromagnetic field. Electromagnetism = a combination of
electricity and magnetism
Light waves do notneed a physical medium like air.
![Page 5: A difficult question, thousands of years in understanding. Very difficult to study, since it cannot be caught, and it is very difficult to measure.](https://reader031.fdocuments.in/reader031/viewer/2022020117/56649d8a5503460f94a70362/html5/thumbnails/5.jpg)
Properties of Light
Frequency – light is caused by the vibrations of electrons
Wavelength – light waves have crests and troughs, just like water waves
Speed – the speed of light depends on what it is traveling through.
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Speed of Light (in a vacuum)
299, 792, 485 m/s ≈ 3 x 108 m/s
186,282 miles per second
671 million miles per hour
Can be slowed if passing through water, glass, etc.
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Types of Light
Most light is invisible, because it has frequencies that our eyes cannot see.
Light with faster frequencies has shorter wavelengths and higher energy
Speed = wavelength x frequency
Wavelength = 3 x 108 m/s ÷ frequency
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Types of light
TypeBallpark Frequen
cy
Ballpark Wavelen
gth
Radio (AM) 106 Hz 300 m invisible
Radio (FM) 108 Hz 3 m invisible
Microwaves & Radar 1010 Hz 3 cm invisible
Infrared 1013 Hz .03 mm invisible
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Types of light
Type Ballpark Frequency
Ballpark Wavelen
gth
Visible 4.4 x 1014 Hz 700 nm Red
4.9 x 1014 Hz 600 nm Orange
5.1 x 1014 Hz 580 nm Yellow
5.8 x 1014 Hz 530 nm Green
6.3 x 1014 Hz 470 nm Blue
6.9 x 1014 Hz 430 nm Indigo
7.4 x 1014 Hz 390 nm Violet
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Types of light
TypeBallpark Frequen
cy
Ballpark Wavelen
gth
Ultraviolet 1016 Hz 3 x 10-8 m invisible
X-Rays 1017 Hz 3 x 10-9 m invisible
Gamma Rays (from
space)1018 Hz 3 x 10-10 m invisible
??? More? Smaller? invisible
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A Spectrum is a continuous range
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Another Diagram
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Notice this backwards (?) diagram
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The NECAP Version
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It’s a Spectrum!
The only difference between types of light is how fast it vibrates (frequency)
Radio waves, visible light, and x-rays are all waves created by vibrating electrons at different speeds
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Light can act like a wave!
It can reflect! Reflection = bouncing off
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Light can act like a wave!
It can refract! Refraction = bending when it passes through
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Light can act like a wave!
It can disperse! Dispersion = separating frequencies of light
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Light can act like a wave!
It can diffract! Diffraction = spreading out and separating (by frequency)
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![Page 21: A difficult question, thousands of years in understanding. Very difficult to study, since it cannot be caught, and it is very difficult to measure.](https://reader031.fdocuments.in/reader031/viewer/2022020117/56649d8a5503460f94a70362/html5/thumbnails/21.jpg)
Summary 1/3
Light is a wave.
Light has frequency and wavelength.
The speed of light in a vacuum is 3 x 108 m/s.
It is the second fastest thing in the universe (only bad news travels faster).
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Summary 2/3
There are many types of light, which all differ only by frequency/wavelength
Faster frequency = shorter wavelength = more energy
In order: Radio, Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, Gamma Rays
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Summary 3/3
Light reflects (bounces off of objects), like on a mirror
Light refracts (bends while passing through objects), like through a glass
Light diffracts (spreads out and separates by wavelength), like making a rainbow