Transcript
In this unit:
1) Properties of light2) Reflection3) Refraction4) Total Internal Reflection5) Optical Fibre
Part 1 – Properties of Light
Light travels in straight lines:
Laser
Light travels VERY FAST – around 300,000 kilometres per second.
At this speed it can go around the world 8 times in one second.
Light travels much faster than sound. For example:
1) Thunder and lightning start at the same time, but we will see the lightning first.
2) When a starting pistol is fired we see the smoke first and then hear the bang.
We see things because they reflect light into our eyes:
Homework
Shadows
Shadows are places where light is “blocked”:
Rays of light
Properties of Light summary
1) Light travels in straight lines2) Light travels much faster than sound3) We see things because they reflect light into
our eyes4) Shadows are formed when light is blocked by
an object
Reflection of Light
The phenomenon of bouncing back of light in same medium from reflecting surface.
ReflectionReflection from a mirror:
Incident ray
NormalReflected ray
Angle of incidence
Angle of reflection
Mirror
ii r
The Law of ReflectionThe Law of Reflection
Angle of incidence = Angle of Angle of incidence = Angle of reflectionreflection
The same !
!!
The incident ray, normal & reflected ray all lie one plane. The incident ray and reflected ray are on opposite side of normal.
Incident ray Reflected ray
Normal
ii r
Refraction• The change in direction of a wave as is
crosses the boundary between two media in which the wave travels at different speeds.
Snell’s Law
nnnnn
1
2
2
1
2211
sinsin
sinsin
Refractive Index
materialinlightofspeedvacuuminlightofspeedn
It also denoted by µ
A A prism is a portion of transparent refracting medium bounded by three rectangular and triangular faces. The angle between the refracting faces is called angle of prism.
The phenomenon of bending of light, when light strike on boundary separating two media at angle of incident greater than critical angle is called as total internal reflection.
Critical Angle
Critical angle is defined as that angle of incidence for which the angle of refraction r is equal to 90o .It is given by C = sin -1 ( )
Optical fibre is a transmitting media just like human hair.
Structure of Optical Fibre
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