Light is represented as a ray that travels in a straight path.
The direction can only be changed by placing an obstruction in the
rays path.
Slide 3
Luminous Sources: objects that emit light Sun, flash lights,
candles Illuminated Sources: objects that are visible as a result
of light reflecting off of it Moon, bicycle reflector Opaque,
Transparent, and Translucent are all used to describe how
illuminated sources are visible
Slide 4
Luminous Flux is the amount of energy that a light emits. Unit:
lumen (lm) A typical 100-W bulb = 1750 lm Illuminance is the rate
at which light hits a surface. Unit: lux (lx) Equivalent to lm/m
2
Slide 5
The amount of light that hits a surface depends on the distance
to the object. In fact it is an..
Slide 6
9090
Slide 7
Light was initially thought to travel at an instantaneous
speed. Galileo was the first to hypothesize that light has a finite
speed. Ole Roemer (Danish astronomer) was the first to find that
light did travel with a finite speed. In 1926 an American
physicist, Albert A. Michelson used a set of rotating mirrors to
measure the speed of light.
Slide 8
Michelsons measure of 2.997996 x 10 8 m/s won him the Nobel
prize in science. The first American ever to accomplish this. Today
the speed of light, c, is given by 299,792,458 m/s. For calculation
purposes, c = 3 x 10 8 m/s Light travels 9.46 x 10 12 km in one
year.
Slide 9
In 1665 an Italian scientist observed that the edges of shadows
are not perfectly sharp. From this observation he realized that
light was diffracted like all waves. In 1678 a Dutch scientist
Christiaan Huygens used this observation to argue the wave nature
of light.
Slide 10
Newton used a prism to pass white light through. Newton called
this arrangement of colors a spectrum.
Slide 11
Since light was now proven to act like a wave, the wave
equation is now applicable to use with light. The range of
frequencies for light are
Slide 12
A. 4.28 x 10 14 Hz B. 4.9 x 10 8 Hz C. 4.28 x 10 5 Hz D. 4.9 x
10 -1 Hz
Slide 13
A. Red, blue, yellow B. Red, blue green C. Magenta, cyan,
yellow D. Magenta cyan, green
Slide 14
White light is composed off all the different colors of the
spectrum. However, a combination of three colors with the correct
intensities will produce white light. These three colors are Red,
Blue, Green. These colors are known as the primary colors
Slide 15
Red BlueGreen Magenta Yellow Cyan
Slide 16
Cyan, Magenta, and Yellow are called secondary colors because
each is a combination of two primary colors. Complimentary colors
are two colors of light that can be combined to make white
light.
Slide 17
The colors of objects are not only determined by the colors of
light they reflect but also the colors of light they absorb. Dyes
and pigments are used to make materials absorb different colors of
light.
Slide 18
The primary pigments are Cyan Magenta Yellow Each pigment only
reflects the color of light it is made of.
Slide 19
A. red B. green C. blue
Slide 20
A pigment that absorbs two colors of light is called a
secondary pigment. Example: green pigment will only allow green
light to reflect, therefore canceling out red and blue Note that
the primary pigments are the secondary colors and the secondary
pigments are the primary colors.
Slide 21
Why do we buy polarized sunglasses? What exactly does it mean
that they are polarized?
Slide 22
Light travels as a transverse wave, which means its particles
vibrate perpendicular to the wave motion. Polarization of light
means to limit the direction in which light is allowed to
vibrate.
Slide 23
In the picture above, the polarizer acts like a doorway, only
allowing light that is traveling in a specific direction
through.
Slide 24
When light reflects off of any surface, the light is polarized
along the plane of the surface. Example: light reflected off a road
becomes horizontally polarized When you wear polarized sunglasses,
this reduces the glare from the cars and the road in front of
you.
