3B Scientific U14600 Optics on magnetic boards - Manual (Page 2)

Exp.4: Real image formed by a
concave mirror
The optical axis is located by means of a
ray which reflects on itself. Two rays of
light, one parallel to the optical axis and
the other through the focal point F, are
made to intersect at the object point
(upright arrow). The reflected rays
intersect at the image point (inverted
arrow).
Exp.5: Focal length of a convex mirror
The centre of curvature C of the concave
mirror is located by means of a ray which
reflects on itself and is extended behind
the mirror. The reflections of two parallel
rays are also extended in the same
manner until they intersect in the focal
point. The distance of the center of
curvature C is twice as long as the
distance of the focus F. f = r/2
In case the rays are non-parallel to the
optical axis, the reflected rays intersect in
a point on an axis which is referred to as
the focal plane. The focal plane passes
through the focal point and is
perpendicular to the optical axis.
Exp.6: Virtual image formed by a
convex mirror
Two rays, one of them parallel to the
optical axis; are made to intersect at the
object point (upright arrow). The
extensions of the reflected rays are drawn
behind the mirror. The virtual image
(inverted arrow) is erect and smaller than
the object.