50
I
n the 17th century, Isaac
Newton and the Dutch
astronomer Christiaan
Huygens both pondered the true
nature of light, and reached very
different conclusions. The problem
they faced was that any theory
about the nature of light had to
explain reflection, refraction,
diffraction, and color. Refractionis the bending of light as it passes
from one substance to another, and
is the reason that lenses can focus
light. Diffraction is the spreading
out of light when it passes through
a very narrow gap.
Before Newton’s experiments,
it was widely accepted that light
gained its quality of color by
interacting with matter—thatIN CONTEXT
BRANCH
PhysicsBEFORE
11th century Alhazen
shows that light travels
in straight lines.1630 René Descartes proposes
a wave description of light.1660 Robert Hooke states
that light is a vibration of
the medium through which
it propagates.AFTER
1803 Thomas Young describes
experiments that demonstrate
how light behaves as a wave.1864 James Clerk Maxwell
predicts the speed of light and
concludes that light is a form
of electromagnetic wave.1900s Albert Einstein and
Max Planck show that light
is both a particle and a wave.
The quanta of electromagnetic
radiation they recognize
become known as “photons.”IS LIGHT A
PARTICLE OR
A WAVE?
CHRISTIAAN HUYGENS (1629–1695)
Light is disturbances in
the ether spreading
out as waves.The corpuscles are
weightless and travel
in straight lines.Huygens thought that...
space is filled with an ether.Newton thought that...
a source of light emits large
numbers of tiny “corpuscles.”Is light a particle or a wave?