Physics 6

ray model of light

ray model of light

A model that represents light as a ray that travels in a straight path, whose direction can be changed only by putting an obstruction in the path

luminous source

An object, such as the Sun or an incandescent lamp, that emits light

illuminated source

an object, such as the Moon, that becomes visible as a result of the light reflecting off it

opaque

A medium that absorbs light and reflects some light rather than transmitting it, preventing objects from being seen through it

transparent

A medium that transmits light and also can reflect a fraction of the light, allowing objects to be seen clearly through it

translucent

A medium that transmits light and also can reflect a fraction of the light, but does not allow objects to be seen clearly through it

luminous flux

the rate at which light energy is emitted from a luminous source; is measured in lumens, lm

illuminance

The rate at which light strikes a surface, or falls on a unit area; is measured in lumens per square meter or lux, lx.

diffraction

the bending of light around a barrier

primary color

red, green, and blue which can be combined to form white light and mixed in pairs to produce the secondary colors: yellow, cyan, and magenta

secondary color

yellow, cyan, and magenta, each of which is produced by combining two primary colors

complementary colors

a color of light, which when combined with another color light, produces white light

primary pigment

cyan, magenta, and yellow, each of which absorbs one primary color from white light and reflects two primary colors; can be mixed in pairs to produce the secondary pigments: red, green, and blue

secondary pigment

red, green, and blue, each of which absorbs two primary colors from white light and reflects one primary color; can be produced by mixing pairs of cyan, magenta, and yellow pigments

polarization

light whose waves oscillate only in a single plane. For a magnet, describes the property of having two distinct, opposite ends, one of which is a north-seeking pole and the other of which is a south-seeking pole

Malus's law

states that the intensity of light coming out of a second polarizing filter equals the intensity of polarized light coming out of a first polarizing filter, times the cosine, squared, of the angle between the polarizing axes of the two filters

specular reflection

a reflection produced by a smooth surface in which parallel light rays are reflected in parallel

diffuse reflection

a scattered, fuzzy reflection produced by a rough surface

plane mirror

A flat mirror, smooth surface from which light is reflected by regular reflection, producing a virtual image that is the same size as the object, has the same orientation is the same distance from the mirror as the object

object

a luminous or illuminated source of light rays that are to be reflected by a mirrored surface

image

the combination of image points in a plane mirror from which the reflected object seems to originate

virtual image

the image formed of diverging light rays; is always on the opposite side of the mirror from the object

concave mirror

a mirror that reflects light from its inwardly curving surface and can produce either an upright, virtual image or an inverted, real image

principal axis

a straight line perpendicular to the surface of a mirror that divides the mirror in half

focal point

the point where incident light rays that are parallel to the principal axis converge after reflecting from the mirror

focal length

the position of the focal point with respect to the mirror along the principal axis

real image

an inverted optical image that is smaller than the object and is formed by the converging of light rays

spherical aberration

the image defect of a spherical mirror that does not allow parallel light rays far from the principal axis to converge at the focal point, and produces an image that is fuzzy, not sharp

magnification

the amount that an image is enlarged or reduced in size, relative to the object

convex mirror

a mirror that reflects light from its outwardly curving surface and produces an upright, reduced, virtual image

index of refraction

for a medium, is the ratio of the speed of light in a vaccuum to the speed of light in that medium

Snell's law of refraction

States that the product of the index of refraction of a medium and the sine of the angle of incidence equals the product of the index of refraction of a second medium and the sine of the angle of refraction.

critical angle

the certain angle of incidence in which the refracted light ray lies along the boundary between two media

total internal reflection

occurs when light traveling through an area with a higher index of refraction to an area with a lower index of refraction hits a boundary at an angle that exceeds the critical angle and all light reflects back into the area with the higher index of refraction

dispersion

the separation of white light into a spectrum of colors by such means as a glass prism or water droplets in the atmosphere

lens

A piece of transparent material, such as glass or plastic, that is used to focus light and form an image

convex lens

a converging lens, thicker at its center than at its edges, that refracts parallel light rays so the rays meet at a point when surrounded by material with a lower index of refraction; can produce a smaller, inverted, real image, or a larger, upright, virtual image

concave lens

A diverging lens, thinner at its middle than at its edges, that spreads out light rays passing through it when surrounded by material with a lower index of refraction; produces a smaller, virtual, upright image.

thin lens equation

states the inverse of the focal length of a spherical lens equals the sum of the inverses of the image position and the object position

chromatic aberration

a spherical lens defect in which light passing through a lens is focused at different points, causing an object viewed through a lens to seem to be ringed with color

achromatic lens

A combination of two or more lenses with different indices of refraction (such as a concave lens with a convex lens) that is used to minimize a chromatic aberration.

nearsightedness

a vision defect in which a person cannot see distant objects clearly because images are focused in front of the retina; can be corrected with a concave lens

farsightedness

a vision defect in which a person cannot see close objects clearly because images are focused behind the retina; can be corrected with a convex lens

incoherent light

light with unsynchronized wave fronts that illuminates objects with an even white light; light whose waves are out of step, with their maxima and minima not coinciding

coherent light

light from two or more sources, whose additive superposition produces smooth wave fronts; light whose waves are in step, with coinciding maxima and minima

interference fringes

a pattern of light and dark bands on a screen, resulting from the constructive and destructive interference of light waves passing through two narrow, closely spaced slits in a barrier

monochromatic light

light having only one wavelength

thin-film interference

a phenomenon in which a spectrum of colors is produced due to the constructive and destructive interference of light waves reflected in a thin film

diffraction pattern

a pattern on a screen of constructive and destructive interference of Huygens' wavelets

diffraction grating

a device consisting of large numbers of single slits that are quite close together, diffract light, and form a diffraction pattern that is an overlap of single-slit diffraction patterns; can be used to precisely measure light wavelength or to separate light of different wavelengths

Rayleigh criterion

states that if the central bright spot of one image falls on the first dark ring of the second image, the images are at the limit of resolution