Download - Physics - Light
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LIGHTReflection of Light
Refraction of Light
Lenses
NATURE OF LIGHT
Light is a form of energy.
Light is a form of wave motion.
The way in which light radiates from its source is similar to the way in which ripples spread outwards across a pond.
NATURE OF LIGHT
Light travels at a speed of 3 x 108 m/s through empty space.
Light can be detected by human eye.
This speed is equivalent to travelling 7 times roundthe Earth in less than a second!
Light travels in straight lines.
Light travels in straight lines.
Light travels in straight lines.
EXPERIMENT TO DEMONSTRATE RECTILINEAR PROPAGATION
Apparatus: 3 card board screens having small holes in their centers. Candle or lamp.
LIGHT RAYS
The path along which light energy travels is called a ray.
A light ray
A bundle of light rays is a beam of light.
Line represents the path along which light travels.Arrow represents the direction in which light travels.
LIGHT BEAMS
3 different types of light beams :
Parallel Beam : Light rays travels from very far away
Divergent Beam : Light rays from a point source (not far away)
Convergent Beam : Light rays meet at a point
REFLECTION OF LIGHT We can see
luminous objects: as they give off light which enters our eyes.Non-luminous objects: as they reflect light from a source to our eyes.
TERMS USED IN THE STUDY OF REFLECTION
A reflecting surface
Any shiny (smooth) surface. E.g a plane mirror
Symbol of a plane mirror
reflecting surface
TERMS USED IN THE STUDY OF REFLECTION
The incident ray
The ray that approaches the mirror.
incident ray
TERMS USED IN THE STUDY OF REFLECTION
The reflected ray
The ray that bounces off the mirror.
reflected rayincident ray
TERMS USED IN THE STUDY OF REFLECTION
The point of incidence
The point where the incident ray meets the mirror.
reflected rayincident ray
point of incidence
TERMS USED IN THE STUDY OF REFLECTION
The normal
The line that is perpendicular (at 90o) to the mirror.
normal
reflected rayincident ray
TERMS USED IN THE STUDY OF REFLECTION
The angle of incidence, i
The angle between the incident ray and the normal.
normal
reflected rayincident rayi
TERMS USED IN THE STUDY OF REFLECTION
The angle of reflection, r
The angle between the reflected ray and the normal.
normal
reflected rayincident rayi r
TERMS USED IN THE STUDY OF REFLECTION
LAWS OF REFLECTION
The angle of incidence is equal to the angle of reflection.
i = r
normal
reflected rayincident rayi r
LAWS OF REFLECTION
The incident ray, the reflected ray and the normal at the point of incidence all lie on the same plane.
We always see all of them on the flat piece of surface.
LAWS OF REFLECTION
IMAGE IN A PLANE MIRROR
The image is virtual.
The image is upright.
The image formed has the same size as the object.
Image cannot be formed on the screen. Light rays do not meet at the image position.It is an imaginary image.
IMAGE IN A PLANE MIRROR
The image is as far behind the mirror as the object is in front of the mirror.
Object distance d1 = Image distance d2
d1d2
IMAGE IN A PLANE MIRROR
The image is laterally inverted (left-to- right inversion)
Left side of the object becomes the right side of the image.
APPLYING THE LAWS OF REFLECTION
To locate image formed in a plane mirror.
EYEO
RAY DIAGRAMS
Step 1 : Locate the image position.
EYE
I
O
RAY DIAGRAMS
Step 2 : Draw reflected rays (connect Image I to eye)
EYE
I
O
RAY DIAGRAMS
Step 2 : Draw incident rays. (connect object O to reflected rays)
EYE
I
O
To draw the mirror image of an object.
APPLYING THE LAWS OF REFLECTION
USING REFLECTION
Periscope
Mirror in meter
Optical testing
Other uses