Newton proposed the corpuscular theory of light to explain the properties of light observed at that time. He believed that light consisted of tiny particles called corpuscles that traveled in straight lines and at high speeds. According to Newton's theory, corpuscles of different colors had different sizes, which explained why prisms separated white light into a spectrum of colors. Newton's particle theory dominated optics in the 18th century despite not being entirely accurate.

1. Nature of Light
Newton’s corpuscular theory
of light
Classe 3 A

2. A long time ago …
Aristotle (384 - 322 B.C.), an ancient
Greek, thought that we see the
world by sending “something” out
of our eye and that reflects from the
object.

3. In the17th century, two scientists had
different views about the nature of light …
Christian Huygens (1629/1695)
Isaac Newton (1643/1727)
No! Light is
particles
Light is
waves

4. In the 17th century, some properties of light
were already known. For example:
• Light has different colours.
• Light can travel through a vacuum.
• Light can be reflected and refracted.
Newton was the “winner”…(at that time!)

5. Why does
light
have
different
colours?
Why does
light travel
in straight
lines?
Why can
light travel
through a
vacuum?

6. Isaac Newton observed that a thin beam of sunlight
hitting a glass prism on an angle creates a band of
visible colors that includes red, orange, yellow,
green, blue, indigo and violet.
This occurred because different colors travel
through glass at different speeds.

7. So he proposed his “particle theory of light”
to explain the characteristics of light.
I think light is
a stream of
tiny particles
called
Corpuscles
(source: “Opticks”, published by Isaac Newton in 1704)

8. 1. Light consists of very tiny particles
known as “corpuscles”. Every
elumiscent source like the sun or a
candle emit these corpuscles.

9. 2. These corpuscles on emission
from the source of light travel in
straight line with high velocity in
all possible directions.

10. 3. When these particles enter the
eyes, they produce image of the
object or sensation of vision.

11. 4. Corpuscles of different
colours have different sizes.

12. Newton’s particle theory of light had a
greater explanatory power than Huygens’
wave theory and dominated optics during
the 18th
century even if it was not correct.