This document discusses the nature of light as an electromagnetic wave, how light interacts with different materials as either luminous or illuminated bodies, the characteristics of light like wavelength and speed, and concepts such as luminous flux, illuminance, luminous intensity, the additive and subtractive properties of light, and how dyes and pigments produce color. It also covers topics ranging from the primary and complementary colors of light and pigments to polarized light and thin film interference.

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