Science8 Unit C Lightand Optics Section2 Lesson4 Mirrors Lensesand Refraction [Autosaved]
Science8 Unit C Lightand Optics Section1 Lesson1 The Challengeof Light
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Transcript of Science8 Unit C Lightand Optics Section1 Lesson1 The Challengeof Light
Science 8Unit C: Light and Optical Systems
Science InAction 8
Our knowledge about light and vision comes from explanations, inventions, and investigations
Section 1.1: Pages 174-181
The Challenge of Light 1.1
Learner Outcome
Students will identify challenges in explaining the nature of light and vision
Light Light is energy Our eyes are able to
see an object only if light is emitted from the object or bounces off it
Light travels in straight lines and needs a direct path
Early Greeks and Chinese used mirrors to refract the light from the sun using mirrors.
Early Light Ideas Pythagoras –
mathematician – tried to explain how we see light
He thought light consisted of beams that came from a persons eyes in straight lines
Problem = If light came from a persons eyes we would be able to see in the dark
This theory was accepted for many years
Euclid Euclid - Greek
mathematician Discovered that when you
shine a beam of light onto a flat mirror, the angle between the incoming beam and the mirror is equal to the angle between the reflected beam and the mirror
Suggested that light travels in straight lines
Light Ideas in the Middle Ages
A.D. 1000, Arab Scientist al-Haytham took up the study of light.
Wrote a book on optics Discovered that light
bounces off objects and then travels to the eye
Pythagoras’s theory was abandoned after his discovery
Newton’s Light Experiment
Rainbow experiment Newton showed that
white light is actually a mixture of different colors of light
As light is passed through a prism, it is split up into many separate colors
Showed that separate colors combined back into white light
A Speedy Discovery Ole Romer in 1676
estimated the speed of light
Albert A. Michelson refined his measurement in an experiment involving 2 mirrors on top of mountains in California in the 1920’s
Page 181
Calculating the Speed of Light - c
Velocity formula v=d/t Or… d=v*t Or… t=d/v
Mirrors apart = 35.4 km
Light was calculated to be 299, 798 km/s
or ~ 300 000 km/s
What was the time it took to travel from one mountain to the other?
Galileo’s Experiment: Later refined by Romer and Michelson
Michelson–Morley experiment
The Properties of Light
1. Travels in straight lines
2. Can be reflected
3. Can bend
4. Is a form of energy
Did you…
identify challenges in explaining the nature of light and vision?
Check and Reflect Questions 2-5, page 181
2. What was Pythagoras’s theory of how we see light?______________________________________________________
________________________________________________________________________________________________________________________________
3. What was the problem with his theory?______________________________________________________
________________________________________________________________________________________________________________________________
Check and Reflect Questions 2-5, page 181
4. What did al-Haytham try to explain?___________________________________________________
______________________________________________________________________________________
5. Based on Michelson’s measurement of the speed of light, if the distance between the sun and the earth is 149 596 000 km, how long does it take light to travel from the sun to the earth?