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What are Lens?
What are Lens?
Piece of glass or other transparent materials with curved sides concentrating or dispersing light, such as for telescopes or camera.
Piece of glass or other transparent materials with curved sides concentrating or dispersing light, such as for telescopes or camera.
What Devices use Lenses?
What Devices use Lenses?
Optical devices that transmits and refracts light
Our eye has lens behind pupils
There are 2 basic lens shapes, converging and diverging.
Diverging/Concave Lenses
Diverging/Concave Lenses
Parallel light rays diverge after refraction from the lens
This lens is thickest at the edges and thinnest in middle
Diverging/Concave Lenses
Diverging/Concave Lenses
Parallel light rays diverge after refraction from the lens
This lens is thickest at the edges and thinnest in middle
Note:
light rays refract twice: entering lens and exiting lens.
Direction of light →
Simplified Path of Light
Simplified Path of Light
Actual path of light shows 2 refractions in lens
Light always cross focal point
Ray diagrams are drawn with only 1 refraction.
From a vertical line through middle of lens.
Note: Light rays refract twice: entering the lens and exiting the lens.
Converging/Convex Lens
Converging/Convex Lens
Parallel lights rays converge at the principal focus (F) after refracting through this lens is thicket in middle and thinnest at the edges.
Image Properties of a Converging Lens
Image Properties of a Converging Lens
As long object is outside of focal point, image: always real and inverted
Only when inside focal point image becomes: virtual and upright
Optical Center
Optical Center
Center of Curvature
Center of Curvature
Convex lens have 2 spherical faces. Each of them forms a part of a sphere.
The centers of these spheres called "Center of Curvature" of the lens. Since there are 2 center. We represent as C1 and C2 👇
Principal Axis
Principal Axis
As mentioned, the principal axis is an imaginary line passing 2 centers of curvatures C1 ad C2 of lens.
Aperture
Aperture
Principal focus of convex lens
Principal focus of convex lens
Focal length
Focal length
Position of F1, F2, 2F1 and 2F2 on principal axis
Position of F1, F2, 2F1 and 2F2 on principal axis
Diagrams in lenses have 4 focus poits in total (2 on each sides), unlike mirrors, which 1.
Rule 1#
Rule 1#
Rule 2#
Rule 2#
Rule 3#
Rule 3#
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