Converging and Diverging Lenses - WordPress.com...Converging (convex) Diverging (concave) Converging...
Transcript of Converging and Diverging Lenses - WordPress.com...Converging (convex) Diverging (concave) Converging...
Converging and Diverging Lenses
What is a Lens?✴ Lens - transparent object used to refract (bend) light in a predictable way
✴ Usually made of glass or plastic
✴Two basic lens shapes:
Converging (convex) Diverging (concave)
Converging LensesThickest in middle and thinnest at edges
Parallel light rays converge through a single point - focal point
FOCAL POINT
FO PA
- exact centre of lensOptical centre (O):
- horizontal line that goes through O and F
Principal axis (PA):
- point after lens where light rays converge
Primary Focus (F): - point before lens that light rays travel through
Secondary Principle Focus (F’):
Converging Lenses
F’2F’ 2F
Diverging LensesThinnest in the middle and thickest at edges
Parallel light rays diverge (spread apart) and do not meet at focal point
Imaging Rules1) Ray parallel to principal axis is refracted through principal focus (F)
2) Ray through secondary principal focus (F’) is refracted parallel to principal axis
3) Ray through optical centre (O) continues straight through without being refracted
Describing Image CharacteristicsS - size (bigger, smaller, same size)
A - attitude (upright, inverted)
L - location (b/w F and 2F, at 2F, beyond 2F, behind lens)
T - type (real, virtual)
Beyond 2F’
At 2F’
Between F’ and 2F’
Important NoteAs object gets closer to lens, image gets larger and further away
For all object positions before F’, image is inverted and real
Lens Characteristics and Images
Many factors affect the characteristics of images:
Lens Type: converging or diverging
Lens Thickness
Lens Optical Density (n)
Lens Thickness
Focal length decreases as lens thickness increases because refracted rays bend more
Lens Optical Density (n)
Focal length decreases as lens optical density increases because refracted rays bend more