Light & Optics

Electromagnetic Waves Electromagnetic waves include: light, radio, microwaves, x-rays, gamma rays, ultra-violet, and infrared radiation. They are generated when electric charges are accelerated. The mathematical description of electromagnetic waves is shown with Maxwell’s equations. These are calculus-based equations we won’t be studying in this course.

Perpendicular Vibrations Electromagnetic waves are made up of two oscillating forms of energy of the same frequency- electrical and magnetic. These fields vibrate in all directions perpendicular to each other and travel as a transverse wave ctromagnetic/index.htmlhttp://micro.magnet.fsu.edu/primer/java/ele ctromagnetic/index.html

Luminous Flux The rate at which light is emitted from a source is called luminous flux. Consider this: waves transfer energy, rate is some value over time; hence luminous flux is energy/ time. Work ideally equals energy. Work / time is POWER. Therefore, luminous flux is a measurement of power and is represented by P. The unit for the power for light is lumen (lm).

Illuminance Illuminance (E) is the measure of the energy received per area. Its units are lumens / meter 2, or lux (lx). The SI unit of this luminous intensity is called the candela (cd).

Illuminance Formula Recall the area of a sphere is 4  r 2. If the energy is transmitted equally in all directions by a point source, the illuminance can be found by: where P represents the luminous flux (power) d is the distance from surface to the source E = P 4  d 2

Transmittance Definitions transparent - material that transmit light waves clearly translucent- materials that transmit light but objects are not clearly seen through it opaque- materials that block or absorb all the light waves that fall on them

COLORSCOLORS colors in the spectrum are associated with a specific wavelength of light colors of light: primary- blue, green, red; secondary- yellow, cyan, magenta

dye- molecule that absorbs certain wavelengths of light and transmits or reflects all other wavelengths (i.e. red dyes absorb blue and green light but reflect red) pigment- a larger particle that has properties like a dye.

Polarized Light- polarized light- light that has passed through a material that allows only one particular plane of wave vibration to pass. arization/polarizationI.htmlhttp:// arization/polarizationI.html

Law of Reflection Angle of incidence equals the angle of reflection. tics/image_e.htmlhttp:// tics/image_e.html tics/mirrorgame_e.htmlhttp:// tics/mirrorgame_e.html

Snell’s Law Snell’s law gives the relationship between angles of incidence and refraction for a wave impinging on an interface between two media with different indices of refraction. The law follows from the boundary condition that a wave be continuous across a boundary, which requires that the phase of the wave be constant on any given plane, resulting in n i *sin  i = n r * sin  r  

Total Internal Reflection When the angle of incidence is equal to the critical angle, all light is refracted at 90° along the surface of the material. When the angle of incidence is greater than the critical angle, all light is reflected within the material instead of refracting out. This is called total internal reflection. ual/Optics/Refraction/refraction.htmlhttp://freespace.virgin.net/gareth.james/virt ual/Optics/Refraction/refraction.html

Concave Mirrors Cf 111fdodi111fdodi = d i =+ d i = 39 Object between the focal point and the center of curvature.

Concave Mirrors Cf 111fdodi111fdodi = d i =+ d i = 28 Object at the center of curvature.

Concave Mirrors Cf 111fdodi111fdodi = d i =+ d i = 22 Object further than the center of curvature.

Concave Mirrors 111fdodi111fdodi = d i =+ d i = -25 Object closer than the focal point. fC

Convex Mirrors 111fdodi111fdodi = d i =+ d i = -10 Object closer than the focal point. fCf

Convex Lens 111fdodi111fdodi = d i =+ d i = 46 Object between the focal point and twice the focal point. f2f f

Object closer than the focal point. Convex Lens 111fdodi111fdodi = d i =+ d i = -19 f2f f

Diagram Summary Draw an incident ray parallel to the center line. The reflected/refracted ray goes through the focal point. Draw an incident ray from the mirror/lens to the focal point through the top of the object. The reflected/refracted ray is parallel to the center line.

Diagram Summary Where the rays meet shows the image. The diagram shows if the image is real or virtual, upright or inverted, smaller or magnified (or the same). If the reflected/refracted lines never meet, the image is a virtual image and can not be projected on paper.

/optics/intro.htmlhttp:// /optics/intro.html University of Aberdeen School of Physics - PX2009University of Aberdeen School of Physics - PX2009

Powers of 10 enceopticsu/powersof10/index.htmlhttp://micro.magnet.fsu.edu/primer/java/sci enceopticsu/powersof10/index.html