This document discusses the positioning of lenses in compound microscopes, telescopes, and eyeglasses or contact lenses. In compound microscopes, the objective lenses are located in the rotating nosepiece near the object and magnify the image, which is then further magnified by the ocular lens located in the part you look through. In telescopes, the objective lens is at the end and collects light from a distance, bringing the image into focus, which is then magnified by the eyepiece lens. Eyeglasses hold two ground lenses in a frame to correct vision, while contact lenses are worn directly on the cornea.
21. Positioning of Lenses in a Compound
Microscope
• A compound microscope has two types of
lenses. It has objective lenses and an ocular
lens.
• The objective lenses are located in the
rotating nosepiece, near the object being
magnified.
• The ocular lens is located in
the part you look through,
which magnifies the image.
Objective Lens
Ocular Lens
22. Positioning of Lenses in a Telescope
• A telescope has two lenses: an objective lens and an
eyepiece lens.
• The objective lens is located at the end of the
telescope, and it collects light from a distance and
then it brings that image into focus.
● The eyepiece lens takes that
focus and magnifies it to make
the image or object look bigger
to the retina.
23. Eyeglasses vs. Contact Lenses
• Eyeglasses are a frame that holds two pieces of glass
or plastic, which have been ground into lenses to
correct refractive errors
• Contact lenses are worn directly on the cornea of the
eye
• Eyeglasses and Contacts help with sight by adding or
subtracting focusing power to the eye’s cornea and lens
