P14 Light Flashcards
what are convex lenses?
they are thicker at the centre than they are at the edges
what is the symbol for convex lenses?
a line with two arrows pointing away from the centre
what do lenses do?
refract light
the light ray bends towards the normal when it enters the lens and away from the normal when it leaves the lens
what are the facts about when parallel rays of light pass through a convex lens?
the central ray passes through the lens without being refracted (it is directly along the normal)
all other rays refract and are focused on a point
what is the principle axis?
the line through the centre of the lens (perpendicular bisector)
what is the principle focus (F)?
where all the parallel rays meet once they pass through the convex lens
what is the focal length?
the distance from the centre of the lens to the principle focus (F)
what is the image like when the object is at least 2 focal lengths away from the lens? (for a convex lens)
the image is:
diminished
inverted
real
what happens with a real image?
the rays ACTUALLY meet at a point
if a screen was placed where the image is, you would see it
what is the image like when the object is between 1 and 2 focal lengths away from the lens?
the image is:
inverted
magnified
real
what is the image like when the object is less than 1 focal length from the convex lens?
the image is:
magnified
erect
virtual
why are dotted lines used when there is a virtual image?
they do not represent the actual path of the rays
how can you tell that an image is virtual?
the rays do not actually meet, they only appear to meet
when does a convex lens produce a virtual image?
when it is used as a magnifying glass
what are the units of magnification?
magnification has no units as it is a ratio
