A difficult question, thousands of years in understanding. Very difficult to study, since it cannot...
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Light Waves
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Transcript of A difficult question, thousands of years in understanding. Very difficult to study, since it cannot...
Light Waves
The Electromagnetic Spectrum
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.
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.
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.
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.
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
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
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
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
A Spectrum is a continuous range
Another Diagram
Notice this backwards (?) diagram
The NECAP Version
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
Light can act like a wave!
It can reflect! Reflection = bouncing off
Light can act like a wave!
It can refract! Refraction = bending when it passes through
Light can act like a wave!
It can disperse! Dispersion = separating frequencies of light
Light can act like a wave!
It can diffract! Diffraction = spreading out and separating (by frequency)
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).
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
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
