basic optical concepts 2.1 Flashcards
what does the geometrical optics approximation assume ?
light travels as rays in a homogeneous medium (same everywhere)
what are wavefronts ?
surfaces of constant phase or constant optical distance from the source
what is a phase ?
point in cycle of wave
e.g. peak of wave
what is optical distance ?
geometrical distance x refractive index
what is the link between wavefronts and rays?
wavefronts in geometrical approximation are always at right angle to rays
why are wavefronts at right angle to rays ?
they are surface of constant optical distance from the objects
what is the paraxial optics approximation ?
. all rays from an object intersect at an image point - this is also known as ideal image formation
what are the two classes of optical systems ?
. some optical systems collect light
e.g. solar panels
. majority of optical systems are image forming optical systems
e.g. eye- positive
what are spherical surfaces ?
. natural shape when two surfaces were together
e.g. ball and socket joint in hip
what do spherical surfaces do ?
. form images of objects
. they also have the ability to take light from objects but can bring light back together
what laws predict ideal image formation ?
.snell’s law and paraxial approximation
. if we know where object is we can know where image is
what do lenses form ?
images
how many surfaces do lenses usually have ?
usually have 2 spherical surfaces
sometimes we can have aspheric lens
what is property of a positive lens ( convex )?
. thicker at centre than edge
. light which passes through it to converge producing real image
. converging lens
. magnify
what is property of negative lens ( concave ) ?
. thinner at centre than edge
. diverging light leaving lens
. image is produced at same side as object
