PPT: Light: Mirrors and Lenses | Science Curiosity Class 8 - New NCERT PDF Download

 Page 1


Light: Mirrors and
Lenses
Page 2


Light: Mirrors and
Lenses
What Are Spherical Mirrors?
Spherical mirrors are shaped like part of a hollow glass sphere with a reflective surface
that can curve inwards or outwards.
Concave Mirror
When the reflecting surface curves inwards, it's
called a concave mirror. Like the inner surface of a
spoon.
Convex Mirror
When the reflecting surface curves outwards, it's
called a convex mirror. Like the outer surface of a
spoon.
Page 3


Light: Mirrors and
Lenses
What Are Spherical Mirrors?
Spherical mirrors are shaped like part of a hollow glass sphere with a reflective surface
that can curve inwards or outwards.
Concave Mirror
When the reflecting surface curves inwards, it's
called a concave mirror. Like the inner surface of a
spoon.
Convex Mirror
When the reflecting surface curves outwards, it's
called a convex mirror. Like the outer surface of a
spoon.
How Spherical Mirrors Are Made
Spherical mirrors are not made by slicing a hollow glass sphere. Instead, they are created by:
Grinding and polishing a flat glass piece into a curved
surface
Applying a reflective coating (like a thin layer of
aluminium)
If coating is on outer curved surface ? concave mirror
If coating is on inner curved surface ? convex mirror
Page 4


Light: Mirrors and
Lenses
What Are Spherical Mirrors?
Spherical mirrors are shaped like part of a hollow glass sphere with a reflective surface
that can curve inwards or outwards.
Concave Mirror
When the reflecting surface curves inwards, it's
called a concave mirror. Like the inner surface of a
spoon.
Convex Mirror
When the reflecting surface curves outwards, it's
called a convex mirror. Like the outer surface of a
spoon.
How Spherical Mirrors Are Made
Spherical mirrors are not made by slicing a hollow glass sphere. Instead, they are created by:
Grinding and polishing a flat glass piece into a curved
surface
Applying a reflective coating (like a thin layer of
aluminium)
If coating is on outer curved surface ? concave mirror
If coating is on inner curved surface ? convex mirror
Characteristics of Images Formed by Spherical
Mirrors
Concave Mirror
Object close to mirror: Image is erect
and enlarged
Object far from mirror: Image becomes
inverted
Size changes with distance - initially
enlarged, then gets smaller
Convex Mirror
Image is always erect
Image is always smaller than the object
(diminished)
Size decreases slightly as object moves
away
Page 5


Light: Mirrors and
Lenses
What Are Spherical Mirrors?
Spherical mirrors are shaped like part of a hollow glass sphere with a reflective surface
that can curve inwards or outwards.
Concave Mirror
When the reflecting surface curves inwards, it's
called a concave mirror. Like the inner surface of a
spoon.
Convex Mirror
When the reflecting surface curves outwards, it's
called a convex mirror. Like the outer surface of a
spoon.
How Spherical Mirrors Are Made
Spherical mirrors are not made by slicing a hollow glass sphere. Instead, they are created by:
Grinding and polishing a flat glass piece into a curved
surface
Applying a reflective coating (like a thin layer of
aluminium)
If coating is on outer curved surface ? concave mirror
If coating is on inner curved surface ? convex mirror
Characteristics of Images Formed by Spherical
Mirrors
Concave Mirror
Object close to mirror: Image is erect
and enlarged
Object far from mirror: Image becomes
inverted
Size changes with distance - initially
enlarged, then gets smaller
Convex Mirror
Image is always erect
Image is always smaller than the object
(diminished)
Size decreases slightly as object moves
away
E x a m p l e s
Mirror Type Image Size Image Orientation Effect of Distance
Plane Mirror Same size as object Always erect No change with
distance
Concave Mirror Can be enlarged or
diminished
Erect when close,
inverted when far
Size changes with
distance
Convex Mirror Always diminished Always erect Size decreases
slightly with
distance