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Mirrors and Lenses
1. Mirrors
Vocabulary
Real image: image that can be formed on a screen.(Projector or cinema)
Virtual image: the image that cannot be formed on a screen.(your image in the
mirror)
Plane mirror: is a mirror with a flat reflective surface.
Concave mirror: is a mirror that has a reflecting surface that curved inward.
Convex mirror: is a mirror that has a reflecting surface that curved outward.
Focal point: is the point in space where parallel light rays meet after passing
through the lens.
Focal length: is the distance between the center of a lens the focal point of the
lens or mirror — the point where parallel rays of light meet.
Types of mirrors
Plane mirror
Image in plane
mirror:
-Has the same size
as the object
-Inverted( right is
left and left is right)
Concave mirror
Image in concave mirror:
the size and direction of the
image depends on the
object's distance from the
mirror.
Convex mirror
Image in convex
mirror:
-Smaller than the
object
-Inverted
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Concave mirror
Convex mirror
Plane mirror
USES OF MIRRORS
Uses of Concave Mirrors:
Shaving and Makeup Mirrors: Objects held close are reflected in a concave mirror as a
magnified image.
Headlights: Concave mirrors are used in motor vehicle headlights to send out strong beams
of light.
Microscopes: Concave mirrors are used in microscopes to collect light from a lamp, shining
it up onto a slide containing a specimen so it can be viewed through a magnification lens.
Telescopes: the concave mirror in the telescope collects light, it shines the light from distant
stars onto a flat mirror allowing a view of faraway stars
Uses of Convex Mirrors:
They are used in sunglasses: Convex mirrors are also used in making lenses of sunglasses.
This is done to help reflect the light of sun away from the eyes of the person wearing the
sunglasses.
Convex mirrors are used in vehicles: Image in convex mirror is always produced up the right
way and it is too smaller in size than the actual size of the object. So the mirror can give a
wide view of the field.
Use in magnifying glass: Two convex mirrors are placed back to back in order to make a
magnifying class.
Use of convex mirror in securities: convex mirrors are placed near ATM’s to allow the bank
customers to check if someone is behind them.
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2. LENSES
Lens: a transparent object that refracts light rays such that they converge or
diverge to create an image.
➢ When the surfaces of a medium are curved, the direction of the normal line
differs for each spot on the surface of the medium.
➢ The images formed can be either real or virtual, depending on the type of lens
and on the placement of the object.
➢ Lenses are commonly used to form images in optical instruments, such as:
• cameras
• telescopes
• microscopes
Convex or Converging Lens
Concave or Diverging Lens
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Lens focal length
Lens focal length tells us:
➢ The angle of view—how much of the scene will be captured
➢ The magnification—how large individual elements will be.
The longer the focal
length, the narrower
the angle of view and
the higher the
magnification.
The shorter the focal
length, the wider the
angle of view and the
lower the
magnification
Other types of lenses