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The Properties of
Light
Light Travels in Straight Lines
Line
Ray
Beam
the paths along which light energy travels
a bundle of light rays
Three ways in which rays are grouped in light beams :
parallel
converging
diverging
These are what happen when light encounters any substance, they can be:
•Reflected
•Absorbed
• Transmitted
• Refracted
A A’
A’A’
the light is reflected if it strikes the surface of a substance and bounces off
the light is absorbed if it strikes the surface of a substance and just disappears
the light is transmitted if the light goes through the material and leaves in the same direction
the light is refracted if the light is bended as it travels through the substance
Reflection of light
Our eyes able to see an object only when the light rays coming from the object enter our eyes.
Objects
Luminous objects are light sources that emit light and we are able to see them directlyExamples : . . . .
Non-luminous objects are seen only because they reflect light from a sourceExamples : . . . .
diffused reflection regular reflection
reflection
the rays are reflected in many different directions
the rays are reflected in parallel directions
rough surface smooth surface
The Laws of Reflection
1. The angle of incidence is equal to the angle of reflection.2. The incidence ray, the reflected ray and the normal at the point of
incidence all lie on the same plane.
reflected rayincidence ray
normal at the point of incidence
plane mirror
angle of incidence angle of reflection
i r
Ray Diagrams and Mirrors
Oobject
iimage
M
plane mirror observer
The position and characteristics of the image formed in a plane mirror can be summarized as follows :
1. It is virtual (it cannot be formed on a screen).
2. It is upright.3. It has the same size as the object.4. It is the same distance behind the mirror as the object
is in front.5. It is laterally inverted (reversed left-to-right).
S2/Gr.8/HO/Physics/Light/[email protected]
