1. Conceptual Physics
Notes on Chapter 27
Light

2. Early Concepts of Light
Up until the time of Newton, most scientists thought that light was a particle. Dutch scientist Christian Huygens said light was a wave.
Then in 1905, Einstein said light was
small particles - massless bundles of
energy that behaved like waves called
photons.

3. Light
Speed of Light
In 1675, a Danish
astronomer named Olaus
Roemer demonstrated that
light travels as a finite speed
Roemer’s Experiment pg. 405
Dutch scientist Huygens looked at Roemer’s data and calculated the speed of light to be 300,000 km/s.

4. Michelson’s Experiment
Light
In 1880, an American scientist named Albert Michelson performed a experiment using a spinning mirror to find the speed of light.
Michelson’s Experiment

5. Light

6. Light
Michelson speed for light (the excepted value today) is 299,920 km/s.
NOTE: We will use Roemer’s rounded
number of 300,000 km/s.

7. Light
FUN FACTS
Light would travel 7.5 times around Earth in one second.
Light takes 8 minutes to travel from the Sun to Earth - a distance of 93,000,000 miles.
Traveling at the speed of light, it would take 4 yrs to travel to the nearest star.

8. Electromagnetic Waves
Light
Electromagnetic Waves
Electromagnetic Spectrum is a continuous range of waves extending from the longest (Radio) and going to the shortest (Gamma).

10. Light
Any material that allows light to pass through in straight lines is said to be transparent.
EX: Glass
Water
Any material that absorbs light w/o reemission is said to be opaque.
EX: Wood
Stone

11. Light
SHADOWS
A thin beam of light is called a Ray. When light rays can not go past an object, a shadow is formed.
Two parts of a shadow are:
umbra: a total shadow.
penumbra: a partial shadow.
EX: Solar and Lunar Eclipses
See pg Fig &

12. Light Light is a transverse wave. White light is Non-polarized.
POLARIZATION
Light is a transverse wave. White light is Non-polarized.
When passed through a
filter (Polarizer) only light
that is moving same as the
filter opening will make it
through.
See pg. 415
Fig

13. Light