3B Scientific Light Box - Manual (Page 7)

7
• Are the angles of incidence equal to the angles of reflection?
The above problem of improper focusing can be resolved by using a Paraboloid (instead of spherical)
or parabolic (instead of circular) mirror.
The caustic curve can also be obtained by allowing light from a bulb to fall directly onto the mirror.
Parabolic Mirror: In a parabolic mirror, distant as well as near rays focus at the same point.
Perform the same experiment as for obtaining the caustic curve.
• Do you obtain another curve or only a point?
• What types of mirrors are used in car headlights, torches, astronomical telescope reflector, etc?
• In the above question, where in relation to the reflector is the radiating device placed?
Convex Mirror - Focus, Center of Curvature: Aim a set of parallel rays onto the mirror. The point
from which the reflected rays appear to be diverging is its focus (can be obtained by extrapolating the
paths of the reflected rays) and the distance of the point from the mirror is the focal length ‘f’.
Reflections From a
Parabolic Mirror
Fig.
M
F
C
Spherical
Aberration
Fig. 3
S