3B Scientific Light Box - Manual (Page 8)

8
• Place a convex lens (of short focal length) in front of the slits and adjust the convex mirror beyond
it until the reflected rays coincide with the incident rays. Draw back these rays to the point where
they appear to meet. This point is the center of curvature of the mirror and the distance of this
point from the mirror is the radius of curvature (r).
• In case co-incidence is not obtained above use the relationship
r v u f
2 1 1 1
= + =
where, f and r are already defined;
u = distance between mirror and point where incident rays appear to meet; and
v = distance between mirror and point where reflected rays appear to meet
Experiments on Refraction:
The basic law of refraction is
r
i
sin
sin
= µ .
Where, µ = refractive index of the medium into which light refracts with respect to the medium the
light is incident from
i = angle of incidence; and
r = angle of reflection
Measurement of
µ - Semi-circular Slab: Allow a single ray to fall normally on the flat side of the
slab. If the emergent ray is deflected, shift the slab (keeping it perpendicular to the incident ray at all
X
C
X’
F
P
Q
L M
Fig. 6
Reflections From
A Spherical
Convex Mirror
Fig.