(i) Define principal focus of a convex mirror.
Ans: Paraxial rays parallel to the principal axis after
reflection at the convex mirror appear to diverge from a point. This point is
the principal focus.
(ii) What is radius of curvature of a convex mirror?
Ans: It is the radius of the sphere of which the mirror
forms a part.
(iii) What is the relation between radius of curvature and
focal length?
Ans: r = 2f
(iv) An object is placed in front of a convex mirror. What
is the nature of the image formed?
Ans: The image is virtual, erect diminished and formed with
in the focus.
(v) What is the use of convex mirror?
Ans: It is used as rear view mirror for motor car. It offers
wide field of view and the image is erect.
(vi) What is the radius of curvature of a plane mirror?
Ans: Infinity
(vii) Aim of Convex Mirror Experiment
To find the focal length of a convex mirror using a convex
lens
(viii) Apparatus of Convex Mirror Experiment
Illuminated object (light box with a cross wire or wire
gauze), convex mirror, convex lens, stands for mounting the mirror and lens,
screen etc.
(ix) Theory of Convex Mirror Experiment
If r is the radius of curvature of the convex mirror, its
focal length, f = r/2
(x) Procedure of Convex Mirror Experiment
The convex lens is placed in front of the illuminated
object, the light box with a cross wire. A screen is adjusted until a clear
image is formed on it. The convex mirror is now placed between the lens and the
screen with its reflecting surface towards the lens. The mirror is adjusted in
position until a clear image of the cross-wire is obtained on the surface of
the light box side by side with the cross wire. The distance between the
position of the convex mirror and the screen is measured. This gives the radius
of curvature r of the mirror. The experiment is repeated with the illuminated
objects at different distances from the lens and the average value of r is
found out. Hence, f = r/2 is calculated.
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