Download Chapter 19 Light, Mirrors, and Lenses

Chapter 19
Light, Mirrors, and Lenses
Section 1
Properties of Light
Pages 550 - 554
What is Light?
• Light is a type of wave that carries energy
through matter or space.
• A source of energy such as the Sun or a light
bulb gives off light waves that spread out in all
directions from the light source.
• A light ray is a narrow beam of light that
travels in a straight line.
Light Travels Through Space
• Most waves travel through a medium. A
Medium is the material through which a wave
travels.
• Light is an electromagnetic wave and doesn’t
need a medium in which to travel.
• Electromagnetic (EM) waves are waves that
can travel through empty space or through
matter
– EM waves travel in – vacuum, air, water, glass, etc
Light and Matter
• Most objects can only be seen if light waves
from another source bounce off of them and
into your eyes.
• The process of light striking an object and
bouncing off is called reflection.
• When light waves strike an object, some of the
waves are absorbed by the object, some are
reflected by it, and some might pass through it.
• What happens to light when it strikes an object
depends on the material the object is made of.
Opaque, Translucent, and Transparent
• All objects reflect and absorb some light
waves.
• Materials are opaque, translucent or
transparent depending on how much light
passes through them.
• Which type of material reflects the least
amount of light?
• Transparent Materials
Opaque, Translucent, and Transparent
• Materials that do not let
light pass through them
are opaque.
• You cannot see other
objects through opaque
materials.
• Some examples include:
– Walls
– Desks
Opaque, Translucent, and Transparent
• Materials that allow nearly all light that
strikes them to pass though are
transparent.
• You can clearly see though these types
of object.
• Some examples include?:
• Glass and clear plastic.
Opaque, Translucent, and Transparent
• Translucent materials allow only some light to
pass through.
• Although object behind these materials are
visible, they are not clear.
• Some examples include?:
• Frosted glass and
• Wax paper.
Color
• The light from the sun may look white, but it is a
mixture of colors.
• Each different color of light is a light wave with a
different wavelength.
• Red light waves have the longest wavelengths
and violet light waves have the shortest
wavelengths.
• White light is separated into different colors
when it passes through a prism.
• The colors in white light range from red to violet.
Electromagnetic Spectrum
Why Do Objects Have Color?
• When light waves strike an object, some waves
are absorbed and some are reflected.
• If an object reflects red waves and absorbs all the
others waves, it looks red.
• An object that reflects all the light waves that
strike it looks white, while one that absorbs all
the light waves looks black.
Primary Light Colors
• Light of almost any color can be
made by mixing different
amounts of the primary colors.
• The primary colors of light are:
red, green, and blue.
• Different colors are produced
where the light beams overlap.
• For example, you see yellow light
when your brain interprets the
combination of green and red
light.
Primary Pigment Colors
• Materials like paint that are used to change to color
of other objects are called pigments.
• The color of the pigment you see is the color of the
light wave that is reflected from it.
• The primary pigment colors are: yellow, magenta
and cyan.
• You can make almost any color by mixing different
amounts of pigments.
Primary Pigment Colors
• Each primary pigment color results when a pigment
absorbs a primary light color.
• For example, magenta pigment absorbs green light
and reflects red and blue light.
• You see this mixture as the color magenta.