Page 129 - Physics - XII

Table for ‘h’

S. Initial reading No. of complete Final reading Additional division moved h =
No. of circular scale rotations made of circular m = a – b if a > b (n × pitch
on convex lens by circular scale scale on the or + m × L.C.)
a n glass slab m = (a + 100) –b (cm)
b if b > a

1.

2.

3.

Mean h= _____ cm

Calculations
1. For water

From tables, we have
Mean value of f = _____ cm
1
Mean value of F = _____ cm
1
1 1 1
Calculate ‘f ’ from = −
f F 1 f 1
f = _____ cm
The radius of curvature of the convex surface of the lens is given by

l 2 h
R = +
6h 2
On putting the values of l and h, the value of R can be calculated.
R
Refractive index of water can be calculated by using the formula 1 f . On putting the values of
R and f, µ can be calculated.

2. For oil
Mean value of f = _____ cm
1
Mean value of F = _____ cm
2
1 1 1
Calculate ‘f ’ from = −
f F f
2 1
f = _____ cm
R
On putting the values of R and f in the relation 1 , refractive index of given oil (µ) can be
calculated. f

Result
The refractive index of water by using convex lens and plane mirror is .... . and the refractive index of given
transparent oil is .....

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