Mirrrors and Lenses, Eye disorders and Corrective Lenses

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