QUARTER FINAL STAGE 2024
YILO KROBO
KOFORIDUA SENIOR HIGH TECH
KNUST SHS
ROUND 4 - TRUE OR FALSE
SECOND SET OF QUESTIONS
PREAMBLE
A short thin object is located on the principal axis of a convex spherical mirror.
1. The image of the object is in the same plane as the object and the principal axis.
ANSWER: TRUE
EXPLANATION:
According to the laws of reflection, the incident ray, the reflected ray, and the normal all lie in the same plane (the plane of incidence).
Since the object and the principal axis define this geometric plane, any ray tracing from the object to the mirror surface stays within it.
Consequently, the virtual intersection of these rays behind the mirror must occur within this very same plane.
2. A line drawn from the top of the object to the top of the image intercepts the principal axis at right angles.
ANSWER: FALSE
EXPLANATION:
A convex mirror always forms a virtual, erect, and diminished image.
The image is located closer to the pole of the mirror than the object is.
Because the image height is smaller than the object height and they are at different horizontal distances from the mirror, a line connecting their top points slopes downward toward the mirror.
It does not intersect the horizontal principal axis at a right angle.
3. The principal axis bisects a line drawn from the top of the object to the top of its image.
ANSWER: FALSE
EXPLANATION:
Both the object and its virtual image are erect, meaning they both stand entirely above the principal axis.
Since the line connecting the top of the object to the top of the image stays completely above the principal axis, the axis does not cross or cut through the line at all, let alone bisect it.
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PRACTICE QUESTIONS
PREAMBLE 1
An object is placed in front of a convex mirror.
1. The image is virtual.
ANSWER: TRUE
EXPLANATION:
The reflected rays diverge.
2. The image is larger than the object.
ANSWER: FALSE
EXPLANATION:
A convex mirror always gives a diminished image.
3. The image is upright.
ANSWER: TRUE
EXPLANATION:
Virtual images from a single mirror are upright.
PREAMBLE 2
An object moves away from a convex mirror.
1. The image moves towards the focal point.
ANSWER: TRUE
EXPLANATION:
For a very distant object the image forms at F.
2. The image gets larger.
ANSWER: FALSE
EXPLANATION:
It gets smaller.
3. The image stays behind the mirror.
ANSWER: TRUE
EXPLANATION:
It is always virtual.
PREAMBLE 3
A convex mirror is used as a car's rear-view mirror.
1. It gives a wide field of view.
ANSWER: TRUE
EXPLANATION:
It diverges light from a wide region.
2. It makes cars look nearer than they are.
ANSWER: FALSE
EXPLANATION:
The small images make them seem farther away.
3. Its focal length is taken as negative.
ANSWER: TRUE
EXPLANATION:
Its focus is virtual.