Telescopes, Optics and the Eye Flashcards
convex/converging lenses?
focus parallel light
the focal length of a convex lens is the distance from the middle of the lens to the point where the light is focused
the focal point is positive
concave/diverging lenses
a concave/diverging lens spreads out parallel light. the light appears to come from a point and the focal point is from the Middle of the lens to where the light appears to be coming from
how do you find the focal length
1) get the lens and a flat white surface
2) find a distant light source and focus an image of it on the screen
3) move the screen and lens until the image is in sharp focus
4) measure the distance from the lens to the screen
how to find the power and what is it measured in?
power of the lens= 1/focal length
what can convex images be described as
smaller, vertically inverted and upright
what can convex lenses be describes as
large, upright and virtual
what is the lens equation?
1/focal length= 1/distance from the lens to the object + 1/distance from the lens to the image
how do refracting telescopes work?
1)the telescope is aimed at an object and light is refracted off the object
2) the light is refracted by the objective lens. the lens is convex so it focuses the light. the lens is large so a lot of light can enter it
3) the light is refracted and magnified by the eye piece lens which is used by an observer to view the image
THE IMAGED ARE REAL LARGER AND VERITICALLY AND HORIZONTALLY INVERTED
how do reflecting telescopes work?
combine lens and motors to form an image of a distant object
used the primary concave mirror to focus the light
secondary plan mirror to change the direction of light by ninety degrees
eye peice lens is a convex lens which magnifies the image
how do the eyes see?
1) light passes through the cornea
2) the pupil controls the amount of light let in
3) the lens refracts the light. the ciliary muscle controls the shape of the lens
4) the refracted light forms an image on the back part of the eye called the retina
5) the light is converted into electrical impulses and is sent along the optic nerve to the brain
what is shortsightedness?
it occurs when the image forms before it reaches the regime
the eyeball is too long
and is corrected by a diverging lens
what is longsightedness
the image forms after is reaches the retina
eyeball too short
corrected by converging lenses
how do lenses work
by refracting light
