Download Lesson 01 - The History of Light and Optics

The History of
Light & Optics
What do we Know?
What things do you know about “Light” all ready?
• What can you tell me about the properties of light?
•
History of Light
•
In groups, open up the
Science in Action 8 textbooks
to page 176 - 181
•
As we read through the next
couple of pages, think about
how our knowledge of light
has evolved and how this
has lead to new discoveries
in our present day?
Pythagoras Theory
•
Pythagoreans believed that light came from our eyes and that
where we looked dictated where light was and what we could
see.
•
WHY WAS THIS OBVIOUSLY NOT THE CASE?
Pythagoras Theory
•
Pythagoreans believed that light came from our eyes and that
where we looked dictated where light was and what we could
see.
•
WHY WAS THIS OBVIOUSLY NOT THE CASE?
•
This theory was
obviously wrong
because then why
couldn’t we see in
the dark
Euclid’s & Ptolemy
•
Euclid suggested that
light traveled in a
straight line… beams of
light
•
Ptolemy described how
light would bend when
it travelled from objects
of different densities
(i.e. from air to glass)
Haytham & Newton
•
Al – Haytham figured
out that it was our eyes
that absorbed light that
was reflected off of
objects to them so that
we could see
•
Newton was able to
show how white light
was a mixture of several
different colours of light
Galileo & Michelson
•
Galileo was interested in optical
devices such as the telescope.
He made several discoveries in
astronomy as he fine-tuned and
improved upon his telescopes.
•
Michelson was able to figure out
the speed of light. He did this by
placing two mirrors on two
different mountain tops and
timing how long it took for light
to travel back and forth.
Your Assignment
•
Again, In groups, open up
the Science in Action 8
Textbooks to page 181
•
In a small group
discussion… please answer
the “Check & Reflect”
questions on that page.
•
We will go over these
questions as a class in 15
minutes.
Check & Reflect Answers
1. What did Ptolemy discover about light?
Ptolemy was the first to discover that light could bend when it
travels from one medium to another with different densities
(i.e. from air to glass).
2. What was Pythagoras's theory of how we see?
Pythagoras believed that light “came out of our eyes” and
that was how we were able to see object in front of us.
3. What was the problem with Pythagoras’s theory?
His theory could not be true otherwise we should be able to
see in the dark
Check & Reflect Answers
4. What did al-Haytham try to explain?
al-Haytham was the first to properly explain how light was
reflected to our eyes and that our eyes received that light
allowing us to see.
5. Based on Michelson’s measurement of the speed of light. If
the distance from the sun to the earth is 149 596 000 km, how
long does it take light to travel from the sun to the earth?
149 596 000 km ÷ 299 798 km = 499 seconds
seconds
499 seconds = 8 min & 19 sec
Today’s Understanding
•
Today we know that light has certain properties
The properties of light are:
- Light is a Form of Energy
- Light can be reflected
- Light travels in straight lines
- Light can be bent
- Light has a top speed (300,000 km/s)
- White light is a combination of different colours
So the big questions is
“How do we see”?
The Big Idea!!!
We can see because…
1)
2)
3)
4)
Light is emitted from a light source
Light then travels to & strikes an object
Light is reflected off of that object to our eyes
Our eyes gather that light to make an image
out of it
We Can See Because…
Next Class!!!
•
We will talking about
rays, ray diagrams,
casting shadows, and the
difference between:
- Translucent
- Transparent
- Opaque