L2: Refraction at Plane Optical Surfaces

what is a shadow

primitive image based on light blocked by an object

what is the simple geometry for the size of the shadow

d/x = h/y

what is an umbra

uniformly dark region of shadow (object blocks all regions of an extended source)

what is a prenumbra

region of shadow where light is partially blocked (gradually gets brighter towards edges)

shadows are dependent on what

distances

Farther away shadow means?

The shadow will be smaller because the object blocks less light.

Closer up shadow means?

The shadow will be larger because the object blocks more light

objects seen through a pinhole are equally?

in focus at all distances (every point on the object acts as a point source through the pinhole)

problems with perfect focus

-too small, not enough light passing, light bends

what is refractive index

property of an optical medium equal to the velocity of light in a vacuum relative to the velocity in the medium

velocity of light in a vaccuum (c )

3 × 10^8

velocity of an optical medium

n = c/v

what does snells law state

for a ray of light passing from one medium to a medium of higher refractive index, the ratio of the sin of the angle of refraction is equal to the ratio of the refractive index of the two media

n’/n = ?

sin i/sin i’

when one of the media is air n=1, —>

n’= sin i/sin i’

what is the largest possible angle of refraction

90 degrees

critical angle definition

The angle of incidence when the angle of refraction is 90^o, and the ray changes from just refracting to total internal reflection

what happens when the angle of incidence exceeds the critical angle

light is reflected at interface, called total internal reflection