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Module 4 - OPTICS
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OPTICS
is the branch of physics which involves thebehaviour and
properties of light, including itsinteractions with matter and the
construction
of instruments that use or detect it. Optics usuallydescribes
the behaviour of visible, ultraviolet,and infrared light. Because
light isan electromagnetic wave, other forms
of electromagnetic radiation such as X-rays,microwaves, and
radio waves exhibit similarproperties.
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MIRRORS
Is an object that reflects light in a way that preserves
much
of its original quality subsequent to its contact with the
mirror. Mirrors are commonly used for personal
grooming or admiring oneself, decoration, and
architecture. Mirrors are also used in scientific apparatus
such as telescopes and lasers, and cameras.
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TYPES OF MIRROR
PLANE MIRROR
A mirror whose surface lies in a plane; it forms an
image of an object such that the mirror surface is
perpendicular to and bisects the line joining all
corresponding object-image points.
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Example :
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Law of Plane Mirrors
States that the image is always the same distancebehind the
mirror as the object is in front of themirror. The image, I, and
the object, O, always lineup along the same normal.
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CONCAVE andCONVEX MIRROR
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CONCAVE MIRROR
A concave mirror has a shape with a thinnermiddle and thicker
sides in relation to a flat plane.People who cannot see objects in
focus at a
distance but can see objects close up use concavelenses to bring
the farther objects in focus.
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MIRROR EQUATION
Where :
f= focal length
do = object distance
di = image distance
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MAGNIFICATION EQUATION
Where:
hi =height image
ho =height object
do = object distance
di = image distance
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SAMPLE PROBLEM
A 4.00 cm tall light bulb is placed a distance of 45.7 cmfrom a
concave mirror having a focal length of 15.2 cm.Determine the image
distance and the image size.
GIVEN:ho = 4.0 cmdo = 45.7 cmf = 15.2 cm
di = ???hi = ???
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SOLUTION:1/f = 1/do + 1/di1/(15.2 cm) = 1/(45.7 cm) + 1/di0.0658
cm-1 = 0.0219 cm-1 + 1/di
0.0439 cm-1
= 1/didi = 22.8 cm
hi/ho = - di/dohi /(4.0 cm) = - (22.8 cm)/(45.7 cm)
hi = - (4.0 cm) (22.8 cm)/(45.7 cm)hi = -1.99 cm
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CONVEX MIRROR
Identification
A convex mirror curves outward toward a lightsource. Other words
for a convex mirror include fish
eye mirror and diverging mirror.
Effects
A convex mirror reflects light outward. Therefore,
the images it produces are distorted. They aresmaller than the
actual object reflected and arealways upright.
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SAMPLE PROBLEM
A 4.0-cm tall light bulb is placed a distance of 35.5 cmfrom a
convex mirror having a focal length of -12.2 cm.Determine the image
distance and the image size.
GIVEN:ho = 4.0 cmdo = 35.5 cmf = -12.2 cm
di = ???hi = ???
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SOLUTION :
1/f = 1/do + 1/di1/(-12.2 cm) = 1/(35.5 cm) + 1/di-0.0820 cm-1 =
0.0282 cm-1 + 1/di
-0.110 cm-1 = 1/didi = -9.08 cm
hi/ho = - di/dohi /(4.0 cm) = - (-9.08 cm)/(35.5 cm)
hi = - (4.0 cm) (-9.08 cm)/(35.5 cm)hi = 1.02 cm
