Page 6 - 10-phy-12 Geometrical Optics

Since the ray passes from denser to rarer medium, so according to Snell's Law

1 = sin i or n = sin r
n sin r sin i

n = sin DBN (1)
sin CBF

In Fig. 12.2.1
mÐDBN = mÐODB (Alternate angles)
mÐCBF = mÐABN (Vertically Opposite angles)

and mÐCBF = mÐOAB (Alternate angles)
Thus relation (1) becomes

n = sin ODB
sin OAB

Since, angle of incidence is very small sinq é tanq

So, n = tan ODB (2)
In DODB tan OAB
In DOAB
tan OBD = OB
OD

tan OAB = OB
OA

Thus equation (2) becomes

DO YOU KNOW? OB
n = OD = OB ´ OA
A car travelling on road
turns around if it moves at OB OD OB
an angle on the thick mud. OA
The mud slows down one
side of the car, and the = OA
path of the car bends. OD

= h1
h2

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