Transcript light - SCHOOLinSITES

LIGHT
CH. 18
What is Light?
• Light is an electromagnetic
wave that travels through
space requiring no medium.
What happens to light when it
strikes a surface?
• Light can be reflected, transmitted,
or absorbed
Distinguish between
• Opaque
• Transparent
• Translucent
•Opaque – Reflects or absorbs all of the light
that strikes it. You cannot see through opaque
materials.
•Transparent – Transmits most light that
strikes it. As light scatters through the
substance this allows you to see clearly what is
on the other side.
•Translucent – scatters light as it passes
through. You can usually see objects on the
other side, but the details of the object are
blurred.
The Color of Objects
• Opaque objects are the color of the light
that is being reflected.
• Transparent and Translucent objects
transmit light so the color you see is the
color transmitted. Ex. If light passes
through stained glass the color you see
coming through the glass is the color of the
stained glass.
Combining Colors
• Primary colors – three colors
combine to make any other color.
You have primary colors of light
and pigments.
• Secondary colors – equal amounts
of two primary colors.
Primary Light Colors
• Red, Blue,Green
• When combined in equal parts they
produce white light.
• So the color you see is the color
that is being transmitted.
Primary light colors
Primary Pigments
• Yellow, Magenta(red),
Cyan(blue)
• When combined in equal
amounts they produce black
• So, the color you see is the
color that is being reflected.
Primary pigments
• Law of reflection – the angle of incidence, what
goes in = the angle of reflection, what comes out
• Focal point – the point through all reflected light
rays pass or meet
• Refraction – the bending of a wave due to a change
of speed of the medium
• Convex lens – a lens that is thicker in the center than
on its edges.
• Electromagnetic wave – no medium required
• Medium – a material in which a wave travels
• Reflection – the process of light striking an object
and bouncing off.
• Concave lens – thicker on the edges than in the
middle
• Lens – a transparent object with at least one curved
side that causes light to bend.
• Focal length – the distance along the optical axis
from the center of a mirror to the focal point.
• Light ray – narrow beam of light traveling in a
straight line
• Opaque – material such as wood and steel
• Translucent – materials such as wax paper
• Transparent – material such as glass or clear plastic
• Primary colors of light – red, green, blue
and when combined make white
• Primary colors of pigment – red, yellow
blue, when combined make black
• Microscope –a combination of lenses used
to magnify small objects
• Telescope – used to examine very large
objects that are far away.
• Camera – uses a convex lens to form an
image on a medium.
• Speed of light – 300 million m/s
Reflection and Mirrors
•
There are two types of reflection from a
surface.
1. Regular reflection – when parallel rays of
light hit smooth surfaces
2. Diffuse reflection – when parallel rays of
light hit a bumpy or uneven surface
Plane Mirror
• Plane mirrors form a virtual image – an
upright image that forms where light seems
to come from. A plane mirror produces a
virtual image that is upright and the same
size as the object.
Plane Mirrors
Concave Mirrors
• Ex. Spoon
• These mirrors can form virtual and real
images depending how the image falls in
relation to the focal point. If the image is
farther away from the mirror than the focal
point the image is real and appears upside
down. If the image is between the mirror
and the focal point the image forms a virtual
image.
Concave Mirrors
Convex Mirrors
• Can only form a real image. A mirror is
curved outward and appears farther away
than it actually is.
Convex Mirrors
Refraction and Lenses
• Refraction occurs due to the change of the
medium’s speed.
• This creates an index of refraction – a
measure of how much a ray of light bends
when it enters that material/medium.
Seeing Light
• You see objects when a process
occurs that involves both your eyes
and your brain
• Convex lenses are used to correct
nearsightedness and. Concave
lenses are used to correct
farsightedness.
Parts of the Eye