Week 10 Flashcards
Rods
a light-sensitive cell of one of the two types present in large numbers in the retina of the eye, responsible mainly for monochrome vision in poor light.
Cones
one of two types of light-sensitive cell in the retina of the eye, responding mainly to bright light and responsible for sharpness of vision and colour perception.
Normal
intersecting a given line or surface at right angles
Angle of Incidence
the angle which an incident line or ray makes with a perpendicular to the surface at the point of incidence.
Angle of reflection
the angle made by a reflected ray with a perpendicular to the reflecting surface.
Specular reflection
the mirror-like reflection of light (or of other kinds of wave) from a surface, in which light from a single incoming direction (a ray) is reflected into a single outgoing direction.
Diffuse Reflection
reflection of light from a surface such that an incident ray is reflected at many angles rather than at just one angle as in the case of specular reflection.
Virtual Image
an optical image formed from the apparent divergence of light rays from a point, as opposed to an image formed from their actual divergence.
Convex
having an outline or surface curved like the exterior of a circle or sphere.
Concave
having an outline or surface that curves inwards like the interior of a circle or sphere.
Index of Refraction
the speed of light in vacuum divided by the speed of light in the medium.
n = c/v
Dispersion
the separation of white light into colours or of any radiation according to wavelength.
Total internal reflection
the complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critical angle.
Critical angle
the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected
Convergent (converging) lens
lens such that a beam of light passing through it is brought to a point or focus
Divergent (diverging) lens
a lens that causes divergence of rays
Presbyopia
long-sightedness caused by loss of elasticity of the lens of the eye, occurring typically in middle and old age.
Myopia
the quality of being short-sighted.
Diffraction
the process by which a beam of light or other system of waves is spread out as a result of passing through a narrow aperture or across an edge, typically accompanied by interference between the wave forms produced.
Polarisation
The direction in which the electrical field of an electromagnetic wave points
Coherent Light
is a beam of photons (almost like particles of light waves) that have the same frequency and are all at the same frequency.
Laser
a device that generates an intense beam of coherent monochromatic light (or other electromagnetic radiation) by stimulated emission of photons from excited atoms or molecules
