Transcript Refraction

( FOR
STANDARD)
BYDEVENDRA KUMAR
GIRIJA SHANKAR
WHAT DO YOU OBSERVE IN THE
PICTURE GIVEN BELOW ?
THE BROKEN EFFECT OF THE
BRUSH AND THE TOY IS DUE TO
REFRACTION.
EFFECT OF LIGHT
WHEN LIGHT FALLS ON AN OBJECT IT IS PARTLY
REFLECTED, PARTLY REFRACTED AND PARTLY
ABSORBED. MAXIMUM REFRACTION OCCURS IN
TRANSPARENT MEDIUM.
REFRACTION IS ...
BENDING OF LIGHT WHEN IT PASSES FROM ONE
MEDIUM TO ANOTHER MEDIUM OF DIFFERENT
OPTICAL DENSITY.
DUE TO CHANGE IN VELOCITY OF LIGHT WHEN IT
PASSES THROUGH MEDIUMS OF DIFFERENT
OPTICAL DENSITIES.
DUE TO CHANGE IN WAVELENGTH OF LIGHT
WHEN IT PASSES THROUGH DIFFERENT
MEDIUMS.
WAVELENGTH OF LIGHT CHANGES WHEN IT PASSES FROM
ONE MEDIUM TO ANOTHER MEDIUM
LIGHT RAY MOVES AWAY FROM THE NORMAL
WHEN
IT TRAVELS FROM DENSER TO RARE MEDIUM.
AIR
r
i
WATER
LIGHT RAY MOVES TOWARD THE NORMAL
WHEN IT
PASSES FROM RARE TO DENSER MEDIUM.
AIR
i
r
WATER
REFRACTIVE INDEX
FOR A GIVEN PAIR OF MEDIUMS WE DEFINE
A CONSTANT FOR REFRACTION KNOWN AS
REFRACTIVE INDEX.
IT CAN BE DEFINED IN TERMS OF….
DEPTH
VELOCITY
SNELL’S LAW
REFRACTIVE INDEX IS DEFINED AS RATIO OF
REAL DEPTH TO APPARENT DEPTH OF OBJECT
IN THE MEDIUM.
NORMAL
O
AIR
WATER
VIRTUAL OBJECT
P
ACTUAL OBJECT
R
VELOCITY OF LIGHT IS DIFFERENT IN DIFFERENT
MEDIUMS.
AIR
GLASS
VELOCITY OF LIGHT IS DIFFERENT IN DIFFERENT
MEDIUM.
AIR
GLASS
REFRACTIVE INDEX OF A MEDIUM IS DEFINED AS
THE RATIO OF VELOCITY OF LIGHT IN VACCUM
TO VELOCITY OF LIGHT IN THE MEDIUM.
µ=c/v
SNELL’S LAW:-
n1 sin θ1=n2 sin θ2
where n1,n2 are refractive indices
of medium 1and 2 respectively
θ1,θ2 are angle of incidence and
angle of refraction
Observe the phenomenon of
refraction when light ray passes from
rarer medium to denser medium.
Click to observe
REFRACTIVE INDEX OF WATER WITH
Sin i
RESPECT TO AIR = ----------Sin r
AIR
i
r
WATER
Observe the phenomenon of
refraction when light ray passes from
denser medium to rare medium.
Click to observe
CLICK TO INCREASE ANGLE OF INCIDENCE
CLICK TO INCREASE ANGLE OF INCIDENCE
CLICK TO INCREASE ANGLE OF INCIDENCE
CLICK TO INCREASE ANGLE OF INCIDENCE
The angle of incidence in the denser
medium for which angle of refraction is
90º is known as “ CRITICAL ANGLE”.
C
Refractive index of air with respect to glass
= sin i / sin r
= sin c / sin 90°
Refractive index of glass with respect to air
= sin 90°/sin c
=
1 / sin c
µ = 1/ sin c
What do you expect if angle of incident is greater than
critical angle.?
To check your answer click ..
MATERIAL
CRITICAL
ANGLE(DEGREE)
DIAMOND
24.5
FLINT GLASS
37
CROWN GLASS
41.1
PLAIN GLASS
41.2
WATER
48.7
ICE
49.8
CLICK TO INCREASE ANGLE OF INCIDENCE
CLICK TO INCREASE ANGLE OF INCIDENCE
CLICK TO INCREASE ANGLE OF INCIDENCE
TOTAL INTERNAL REFLECTION
WHEN THE ANGLE OF INCIDENCE IN THE
DENSER MEDIUM IS GREATER THAN THE
CRITICAL ANGLE THE RAY UNDERGOES TOTAL
INTERNAL REFLECTION.

 THAT IS ,ALL THE INCIDENT LIGHT IS
REFLECTED AND NO REFRACTION OCCURS.
TOTAL INTERNAL REFLECTION HAS
MANY PRACTICAL APPLICATIONS:
SPARKLING OF DIAMOND
RAINBOW
FORMATION
OPTICAL FIBRE
MIRAGE
PERISCOPE AND
BINOCULAR(PRISM)
Refraction of Light by Diamonds
The brilliance of diamonds is due to their high refractive index, which
is about 2.4. The skill of the gem-cutter lies in angling the facets of
the stone so that each light ray entering it is reflected many times
before it emerges again. The refractive index is slightly different for
each colour of light, so the light is split into its coloured components,
giving rise to the multicoloured “fire” of diamonds.
MIRAGE
MIRAGE IS FORMED WHEN LIGHT PASSES FROM
COOLER AIR TO WARMER AIR AND IS BENT
TOWARDS THE HORIZONTAL LINE OF VISION AND
EVENTUALLY IT IS MADE TO TRAVEL UPWARDS BY
TOTAL INTERNAL REFLECTION PRODUCING A
VIRTUAL IMAGE.
OPTICAL FIBRE
Fibre-Optic Cable
A bundle of optical fibres passes easily through the eye of this
needle. Fibre-optic cables are rapidly replacing bulky copper-wire
cables in the telecommunications industry. A single pair of such
cables can carry over a thousand conversations simultaneously.
Binoculars
Binoculars
Binoculars present a different view to each eye to enable a user to perceive
depth. Each half of a pair of binoculars is essentially a telescope; however,
binoculars often incorporate prisms so that they are more compact than a
telescope of comparable power.
TO KNOW MORE ABOUT
REFRACTION VISIT OUR
WEBSITE “ OPTICA”
Mr. V. K SODHI
ENCARTA
.
Freespace.virgin.net/garethjames/virtual/
optics/Refraction/refraction.html
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