astrophysics: lenses

how do lenses change the direction of light rays?

refraction

finish the sentences:

converging lenses are [], and cause rays of light to [] [] [] [].

convex, bend towards each other

a lens causes parallel, non axial rays to do what?

converge somewhere else on the focal plane.

when is an image magnified by a lens?

when the image is further from the lens axis than the object.

when is an image diminished by a lens?

when the image is closer to the lens axis than the object

what is a real image?

when light rays from an object are made to pass through another point in space

what is a virtual image?

when the light rays that create the image appear to come from a different point in space.

finish the sentence:

if the object is [] than the focal length away from the lens, the image is [] and [].

further, real, inverted

finish the sentence:

if the object is [] than the focal length away from the lens, the image is [].

closer, virtual

what is the lens equation?

1/f = 1/u + 1/v

what do the terms in the lens equation mean?

u = distance from object to lens axis

v = distance from image to lens axis

f = focal length

for v in the lens equation, when is it positive and when is it negative?

v is positive when the image is real, and v is negative when the image is virtual