Page 154 - Physics_Form_2

Physics for Secondary Schools
7. Use dashed lines to extend
the reflected rays behind the
mirror until they intersect.
The point of intersection is
the image point of the top of
the object.
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8. Use an arrow to draw the
image by joining the point
of intersection of extended
rays and the principal axis.
9. Measure the image distance
v, the object distance u, the
image height, h and the
i
object height, h Note that,
.
o
distances measured behind
the mirror are considered to
be negative.
10. Repeat Steps 3 to 9 for
different positions of the
object.
11. Summarise the results in a
table.
Questions
(a) What are the characteristics
of the images formed by a
convex mirror?
(b) Do the characteristics of the
image formed by a convex
mirror change with the change
of object position?
From this activity, we observe
that the image of an object in
front of a convex mirror will be
located behind the convex mirror.
Furthermore, the image will be
upright, reduced in size and virtual.
148
Physics Form 2 Final.indd 148
Example 4.4
An object 5 cm long is placed on and
perpendicular to the principal axis of a convex
mirror of radius of curvature 20 cm. Use a
scaled diagram to find the position, size and
nature of the image when the object is 10 cm
from the pole of the mirror.
Solution
The height of the object is 5 cm, the object
distance is 10 cm, the radius of curvature is
20 cm, and the focal length is 10 cm .
Scale: 1 cm represents 5 cm.
From the scale:
Height of object = l cm, object distance =
2 cm and focal length 2 cm
1. Draw a convex mirror with the pole P.
2. Locate the focal point and object position
by using the provided values.
3. Draw any two of the rays stated in the laws
of reflection for a convex mirror as shown
in Figure 4.28.
O A
1 cm N
2 cm P 0.5 cm h i F C
v
1 cm
4 cm
Figure 4.28
4. The object’s image is constructed by
considering the reflection of the rays OA
and ON. After reflection, the ray OA appears
Student’s Book Form Two
25/10/2025 10:27