Mirrrors and Lenses, Eye disorders and Corrective Lenses
MIRRORS AND LENSES
Spherical Mirrors are of
Ans : Two types
Concave mirror
Ans: Reflecting surface curved inward
Convex mirror
Ans : Reflecting surface curved outward
CONCAVE MIRROR CAN BE USED
As a shaving mirror
Reflector in solar cooker
Reflector in astronomical telescope
Search light and head light of automobiles
Used by dentists and ENT specialists
Used as burning glass
Used in torches
CONVEX MIRROR CAN BE USED AS
Rear view mirror in automobiles
Device to check theft in shops
The mirror forms a virtual or real image depending on the position of the object
Ans : Concave mirror
LENS
A transparent medium bounded by two surfaces atleast one of which is curved surface is called
Ans: Lens
The lens thicker at the middle than in edges is called
Ans: Convex Lens
The lens thicker at edges than in the middle
Ans: Concave lens
The unit of power of lens
Ans: Dioptre
Power and focal length of convex lens
Ans: Positive
The power and focal length of concave lens
Ans: Negative
Lens in human eye
Ans: Convex lens
Image formed in concave lens
Ans: Virtual and erect
ALTERNATIVE NAMES
Converging lens - Convex lens
Diverging fens - Concave lens
Converging mirror - Concave mirror
Diverging mirror - Convex mirror
Image formed in Convex lens
Ans: Real and inverted
The shortest distance for clear vision is
Ans: 25cm
Twenty - Twenty means
Ans: Perfect vision
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EYE RELATED DISORDERS AND THE LENSES USED
Myopia/Shortsightendness
Can be corrected by using
Ans: Concave lens
Hypermetropia / long sightedness
Can be corrected by using
Ans: Convex lens
Both Myopia and hypermetropia
Can be corrected using
Ans: bifocal lenses
Astigmatism
Can be corrected by using
Ans: cylindrical lens
Presbyopia
Can be corrected by
Ans: convex lenses
EXTRA POINTS
Persistence of vision of human eye
Ans: 1/16 seconds
Magnification
Ans: height of image / height of the real object
Mirror equation = 1/u1/v=1/f
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