Download Thursday, March 12

DAILY QUESTION
March 12, 2009
1. State the law of
reflection.
Agenda
3/12/09
• Daily Question
• Turn in: Electromagnetic Sign
• Brain Pop – “Electromagnetic Spectrum”
• 15-3 Notes
• Brain Pop – “Color”
Assignments:
1. 15-2/3 Worksheet due 3/13
Another model for light is
the light ray
• It is used to describe:
– Reflection
– Refraction
• A light ray is:
– An imaginary line running in the direction that
the light travels
– It is in the same direction of wave travel or the
path of the photon
• The study of light in cases in which light
behaves like a ray is called geometrical
optics
• Using light rays, one can trace the path of
light in geometrical drawings called ray
diagrams
When a beam of light is reflected,
the path:
Of each light ray in the beam
changes from its initial direction to
another direction
• If the surface is rough:
– Light striking the surface will be reflected at all
angles
• Reflection of light in random directions is called
diffuse reflection
• If the surface is smooth:
– All the light hitting the mirror from one
direction is reflected together into a single
new direction
• The new direction of the light rays is
related to the old direction in a definite way
– The law of reflection states:
The angle of incidence equals the angle of reflection
Flat mirrors form virtual images by reflection.
• The image that you see results from:
the apparent path of the light rays, not an
actual path.
– An image of this type is called a virtual image
• Curved mirrors can distort images.
• Curved mirrors still create images by
reflecting light according to the law of
reflection. But:
– Because the surface is not flat, the line
perpendicular to the mirror points in different
directions for different parts of the mirror
• Concave Mirrors
• Convex Mirrors
– Mirror that bulges out
– Two light rays that start
out parallel are reflected
into different directions
– Image is stretched out
– Mirror that are
indented
– Reflect two parallel
rays in toward one
another
– Image is compressed
• A concave mirror can form two kinds of
images:
– Virtual image
– Real image
• A real image results when:
– Light rays from a single point of an object are
focused onto a single point or small area
• The primary difference between a real and
a virtual image is:
– With a real image, light rays really exist at the
point where the image appears
– A virtual image appears to exist in a certain
place, but there are no light rays there
• The different wavelengths of visible light
correspond to many of the colors that you
perceive.
• Objects have color because:
– They reflect certain wavelengths
– White light from the sun actually contains light
from all the visible wavelengths of the
electromagnetic spectrum
• Colors may add or subtract to produce
other colors.
• Black is:
– Not really a color at all
• It is the absence of color