Page 89 - Physics - XII

Radius of curvature of surface of the convex lens
Pitch of the spherometer = _____ cm
Least count of the spherometer = _____ cm
AB = _____ cm
BC = _____ cm
CA = _____ cm

AB BC CA+ +
l = = _____ cm
3

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

1.

2.

3.

Mean h= _____ cm.
Calculations

From tables we have
Mean value of f = _____ cm
1
Mean value of F = _____ cm
1 1 1
Calculate ‘f ’ from
f F 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 value of l and h, calculate the value of R.
R
Refractive index of water can be calculated by using the formula 1 f . On putting the value of R
and f, µ can be calculated.

Result
The refractive index of water by using convex lens and plane mirror is .......... .

Precautions

1. The parallax should be removed tip to tip.
2. The convex lens of a large focal length should be used.

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