IDENTIFICATION OF LENS, PLUS AND MINUS, SPHERICAL & CYLINDRICAL LENS || लेंस की पहचान कैसे करें ||

Identification of a lens -

Convex lens -

1. It is thick in the center and thin at margins. 

2. Convex lens is a magnifying lens, objects appear bigger in size. 

3. If we move a lens the image moves in opposite direction. 

4. It is denoted by PLUS(+)  sign

5. It is used to correct hypermetropia and presbyopia. 

Concave lens -

1. It is thin in the center and thick at margins. 

2. It is a minifying lens, objects appear smaller in size. 

3. If we move a lens the image moves in same direction. 

4. It is denoted by MINUS(-)  sign. 

5. It is used to correct myopia.

 

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Both convex and concave lenses are of two types :

1. Spherical lens -

i. Movement of images can be seen in all direction. 

ii. If we rotate a lens, there is no distortion of image. 

2. Cylindrical lens -

i. Movement of image can be seen only in one direction, at right angle to its Axis. There is no movement of image along the axis of lens. 

ii. If we rotate a lens, there is distortion of image.