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• Electromagnetic waves
• it travels through a vacuum
• Are waves that have an electric and
magnetic field
• It is a transverse waves
• Vibrates perpendicular to the direction
that they are traveling
• Newton: light is a particle (corpuscles)
• Young: light is a wave
• Einstein: light is a particle (photon)
• Broglie: Dual-Nature of Light
• Maxwell: Electromagnetic Theory of Light
• Incandescence is the emission of light
from "hot" matter (T ≳ 800 K).
• Luminescence is the emission of light
when excited electrons fall to lower
energy levels
(in matter that may or may not be
• The speed of light in a vacuum is a universal
constant in all reference frames.
• The speed of light in a vacuum is fixed at
299,792,458 m/s by the current definition of
the meter.
• The speed of light in a medium is always slower
the speed of light in a vacuum.
• The speed of light depends upon the medium
through which it travels. The speed of anything
with mass is always less than the speed of light
in a vacuum.
• The amplitude of a light wave is
related to its intensity.
• Intensity is the absolute measure of
a light wave's power density.
• Brightness is the relative intensity
as perceived by the average
human eye.
• The frequency of a light wave is related to its
• Color is such a complex topic that it has its own
section in this book.
• Monochromatic light is described by only one
Laser light is effectively monochromatic.
There are six simple, named colors in English (and
many other languages) each associated with a band
of monochromatic light. In order of increasing
frequency they are red, orange, yellow, green, blue,
and violet.
Light is sometimes also known as visible
light to contrast it from "ultraviolet light" and
"infrared light"
Other forms of electromagnetic radiation
that are not visible to humans are sometimes
also known informally as "light"
• Polychromatic light is described by many
different frequencies.
Nearly every light source is polychromatic.
White light is polychromatic.
•The wavelength of a light wave is
inversely pro
Light is often described by it's wavelength
in a vacuum.
Light ranges in wavelength from 400 nm on
the violet end to 700 nm on the red end of
the visible spectrum.
portional to its frequency.
•An object reflects light that
matches colour of the object
and it absorbs all other colours
of light
• Not actually white
• Made up of millions of colours
• Light and sound are energies.
• Different colours of light are light waves
having different frequency
• Dispersion, in wave motion, any phenomenon
associated with the propagation of individual
waves at speeds that depend on their wavelengths.
• Monochromatic light: single color
•Polychromatic light: many colors
• Different colours of light have same
speed in air but when they hit the
glass prism, different colours of light
have different speed in glass prism
• RED has the maximum speed
• VIOLET has minimum speed
• Dispersion of light
 Splitting of white light into its constituent
• Spectrum
Band of colours formed by dispersion
• In glass or any medium (other that air)
different colours travel at different speeds