Introduction Flashcards
Point sources
Emit light waves in all directions (ie. 360 degrees) equally if the medium is homogenous
Light rays
They are perpendicular/ orthangonal to the light wavefront Wavefront = circles pebbles make
Bundle
Collection of rays/wavefronts from a single source
Pencil
Cross-section of a bundle and its point source
Diverging pencil
See image
Light travels
Light will travel L to R
Converging pencil
See image
Parallel pencil
Made when one is very far away from point source of light Optical infinity - more than 20 ft.
Extended object
Made of an infinite number of point sources Each point emits divergent light rays
Ideal imaging system
Outgoing (diverging) wavefronts from a point source, converge to a point called the image point
Which laws are the basis of geometric optics?
- Rectilinear propagation of light 2.neighboring rays of light are independent 3. Law of reflection 4. Law of refraction
Rectilinear propagation of light
Idea that light travels linearly if media is homogenous
Crepuscular rays
Ex. Sunbeam - beams of light seem to radiate from sun
Neighboring light rays are independent
Alight rays from an infinitely distant light source travel parallel to one other through space Ie. If 2 rays converge or enter a space, that doesn’t affect the 3rd ray
Law of reflection
The angle of incidence (i) = the angle of reflection (i’)
What happens when light travels from a less dense to a more dense media?
The velocity decrease NOTE: density directly affects how light travels through the medium
Indices of refraction you must know
n(air) = 1 n(water) = 1.33 [same as aqueous humor and vitreous of the eye] n(lens) = varies
Law of refraction
n sin i = n’ sin i’ [snell’s law] Greater the differnce between the 2 n, the more bending of light When n = n’ -> no bending of light When n > n’ -> light bends away
Left side of optical system
= in front = anterior
Right side of optical system
= behind = posterior
Object distance
Measured from the optical system to the object
Image distance
Measured from the optical system to the image
Focal point
Point where parallel light (from infinity) is brought into focus by the lens
Focal length
Distance from lens to its focal point
Negative distance
Image/ focal point etc. is opposite the direction of light Typically = in front/ anterior = (-) because light travels R->L Distances posterior/ behind lens are positive
How our eye sees images
