LIGHT
UNIT C
Sections 1 & 2

Early ideas
Pythagoras - eye beams
Euclid - light straight lines
al-Haytham - vision, light bouncing, travels to eyes.
Newton - white light made up of colours.

1920s
Albert Michelson
Mirrors on two mountain tops (35.4 km apart).
Timed beam
= 299 798 km/s

Devices
Microscopes - Hans & Zachariah’s Jansen, van Leeuwenhoek (later)
Telescopes - Galileo

Rays diagrams help explain how light travels from a source.
They also help explain intensity or lack thereof.

Sketch a candle with the light reaching an eye (p 190)

Eye Sketch

• Add distance and explain intensity with your sketch
• Explain how shadows work and grow with ray patterns.

Define (p 191)

• Transparent
• Translucent
• Opaque
• Using the candle sketch, what is happening to the light?

Explain luminous and non luminous with a sketch and ray diagrams.

Sketch (p193)

• Reflection of a predictable pattern compared to a diffuse one.
• What items would produce both?

P196, 197, 198
Concave mirrors
Object inversion and focal points

Questions

As you moved the candle around, describe the reflection's properties

• when it’s further away than 2F,
• between 2f and F
• closer than f
• on the other side of the mirror?

Refraction
Change of speed bends light towards the normal. The denser the medium, the more light slows (bends).

Concave versus convex lenses (p 204+)

Go back to simbucket and see how the candle’s image relates to the lens.