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Wize University Physics Textbook (Master) > Wave Optics

Light Waves

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Light Waves



Light is a type of electromagnetic wave, or electromagnetic radiation (EMR).

  • Electromagnetic waves are produced through the interaction of oscillating electric and magnetic fields.
  • Unlike mechanical waves, electromagnetic waves do not need a medium to propagate. They can travel through a medium (clear materials like water or glass), or through a vacuum!










The speed of light traveling in a vacuum is:

 c=3.00×108  m/s \boxed{ \ c = 3.00 \times 10^8 \ \ m/s \ }

Thus, the wave equation for light in a vacuum is:
 c=λf \boxed{ \ c=\lambda f \ }


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There is a whole spectrum of electromagnetic radiation, for the entire range of frequencies and wavelengths that light can have:




Visible light is just a small portion of the spectrum that our eyes can see,
from waves of wavelength 760 nm (red)\bct{760 \ nm\ (\textbf{red})} to 390 nm (violet)\bcfi{390 \ nm\ (\textbf{violet})}.










Wize Concept
Since the speed is constant, the wavelength and frequency are inversely proportional. This means that :
  • high frequency = short wavelength
  • low frequency = long wavelength




Wize Tip
Higher frequencies (shorter wavelengths) give us higher energy. The oscillations get more dense, and more energy is transferred by the light wave.

Practice: Different Types of Electromagnetic Radiation

Rank the following types of electromagnetic radiation from lowest to highest energy.

Radio Waves, Infrared Radiation, X-rays, Microwaves, Visible Light, UV Radiation
Practice: Properties of Light Waves

Match the following with their definitions:
A.
...sound wave or a light wave.
B.
...the wavelength decreases.
C.
...about 580 nm.
D.
...lower frequency.
E.
...about 400 nm.
F.
...gamma rays.
G.
...radio waves.
H.
...a light wave.
I.
...a sound wave.
J.
...highest frequency.
K.
...color.
L.
...pitch.
M.
...visible light.
N.
... about 700 nm.
O.
...wavelength increases.
P.
...compression waves, they need a medium to travel through.
Q.
...UV light.
R.
...lowest frequency.
S.
...light wave.
T.
...EMR, they don't need a medium to travel through.
U.
...higher frequency.
Light wave are...
Sound waves are...
For light waves, frequency increases when...
For light waves, frequency decreases when...
The speed is constant in vacuum for a...
The speed depends on the properties of the medium for a...
The wavelength of red light is...
The wavelength of blue light is...
The wavelength of sunlight is...
The wave that can travel through opaque materials is...
The wave that can only travel through transparent materials is...
The frequency of sound gives its...
The frequency of light gives its...
Red has longer wavelength and...
Violet has shorter wavelength and...
Microwaves have a longer wavelength than...
X rays have a higher frequency than...
Gamma rays have the...
Radio waves have the...
The highest energy is carried by...
The lowest energy is carried by...