Nature of LightNewton’s corpuscular theory

of light

Classe 3 A

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.

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

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!)

Why does light have different colours?

Why does light travel in straight

lines?

Why can light travel through a vacuum?

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.

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)

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

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

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

4. Corpuscles of different colours have different sizes.

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.