1.
Ch 16
Light Waves

2.
Light
 We see objects because light is either
emitted or reflected by the object

3.
Light
 Light is an electromagnetic wave that the human
eye can detect
 Light has wavelengths that range from 400 nm
(violet) to 700 nm (red)
 The speed of light is 3 EE 8 m/s

4.
Luminous Body
 Emits light waves
 Ex: the sun

5.
Illuminated Body
 Reflects light waves
 Ex: the moon

6.
Luminous Flux (P)
 The rate at which light is emitted from a
source
 It is measured in lumen (lm)

7.
Illuminance (E)
 The amount of light that is reflected
E= P
4 πd 2
 Units are lm/m2 or lux (lx)

8.
Luminous Intensity (I)
 Luminous flux that falls on one square
meter of a sphere one meter in radius
I= P
4π
 Units are candela (cd)

9.
Types of Materials

10.
Transparent
 Transmits light
without distortion
 Ex: crystal clear water

11.
Translucent
 Transmits light but the
image is distorted
 Ex: lampshade

12.
Opaque
 Transmits no light
 All light is absorbed or
reflected
 Ex: brick

13.
White Light
 Produced by adding the colors red, blue and
green
 This is called the additive process
 Red, blue and green are called the primary light
colors

14.
Mixing Light Colors
 Red and Green =  Yellow
 Blue and Green =  Cyan
 Red and Blue =  Magenta

15.
Complementary Light Colors
 Yellow and Blue  Produce white light
 Cyan and Red
 Magenta and Green

16.
Dyes and Pigments
 Dyes are molecules that dissolve in liquids
to form colored solutions. They absorb
certain wavelengths and reflect others.
 A pigment also absorbs certain
wavelengths and reflects others, but they
are larger and mix to form suspensions.

17.
Dyes and Pigments
 The absorption process of light forms colors by
the subtractive process

18.
Primary Pigments
Absorb one color from white light and reflect 2 colors
 Yellow absorbs Blue  Reflects red and Green
 Magenta absorbs  Reflects Blue and Red
Green
 Reflects Blue and Green
 Cyan absorbs Red

19.
Secondary Pigments
Absorb 2 colors from white light and reflect one color
 Red absorbs Green  Reflects Red
and Blue (Cyan)
 Green absorbs Red  Reflects Green
and Blue (Magenta)
 Reflects Blue
 Blue absorbs Red
and Green (yellow)

20.
Complementary Pigments
 Produce black light
 Black is not a color just the absence of
light
 No light is being reflected
 Note: The primary light colors are the
secondary pigments and vice versa

21.
What color would a yellow banana
appear if it is hit with green light?
 Answer:
 Green, yellow can reflect red and green,
but there is only green light hitting it.

22.
What color would a yellow banana
appear if it is hit with blue light?
 Answer:
 Black, the yellow absorbs blue light so
there is no light to reflect

23.
What color would a yellow banana
appear if it is hit with cyan light?
 Answer:
 Green, the yellow absorbs blue light
 Cyan – Blue = Green

24.
Polarized Light
 Light that only
vibrates in one plane.
 Polarized light will
only pass through a
polarized filter if it is
parallel to the
vibrating light

25.
Thin Film Interference
 The beautiful colors
are caused when light
reflects off of 2
surfaces
 Example: Oil and
water or the 2 layers
of a bubble