Refraction of lenses and imaging characteristics - Inverted Metallographic Microscope
Refraction of lenses:
A. Types:
(1) Convex lenses (converging lenses) : The middle lens is thicker than the lenses at the edges. There are biconvex, plano-convex and concave lenses.
(2) Concave lenses (diverging lenses): The middle lens is thinner than the lenses at the edges. There are biconcave lenses, plano-concave lenses, and convex-concave lenses.
B. Imaging of convex lenses:
(1) Light refracted from a parallel principal axis passes through the focal point.
(2) Light passing through the focal point is refracted parallel to the principal axis.
(3) Light passing through the centre of the lens is not refracted.
C. Imaging properties of concave lenses:
(1) Light parallel to the principal axis is refracted and directed to its own focal point.
(2) Light aimed at the opposite focus is refracted and directed parallel to the principal axis.
(3) Light passing through the centre of the mirror is not refracted.
D. Characteristics of an image:
(1) The closer the object is to the focal point, the larger the image is, and the farther the distance between the images.
(2) The eye can see the real image, can also see the virtual image; paper screen (light screen) can only find the real image.
(3) The eye to see the virtual image must be from the lens to see.
(4) The imaging properties of a convex lens are similar to those of a concave mirror; the imaging properties of a concave lens are similar to those of a convex mirror.
(5) A convex lens can produce either a real or an imaginary image; a concave lens can have only an imaginary image. The virtual image of a convex lens must be a magnified orthostatic virtual image; and must be behind the object (not necessarily behind the focus)
(6) The virtual image of a concave lens must be a reduced orthogonal virtual image; and must be in front of the object (must be in the focus)
(7) The dividing point between a solid image and an imaginary image: the focus, and between an orthogonal and an inverted image: the real and the imaginary. Dividing point between magnification and reduction: twice the focal length position (2F)
(8) A real image must be inverted and an imaginary image must be upright.
