48 terms

Honors Physics Chapter 7

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Light
small portion of the electromagnetic spectrum that our eyes are capable of seeing
Electromagnetic Spectrum
complete range of radiation produced by accelerated charged particles
Cosmic, Gamma, Ultraviolet, and X rays
high frequency and harmful
Light, Infrared, and Radio Waves
low frequency and harmless
Velocity of Light
all travel at 3x10^8 m/s
Light year
distance that light travels in one year, used to measure extremely large distances like the distance to stars
Production of Light
all atoms have electrons in distinct energy levels. When atoms absorb energy, electrons move to higher energy levels. In all substances, the electrons return to lower energy levels and give off energy in form of light
3 means of atoms becoming excited
heat which occurs in a regular incandescent bulb, electricity through a gas which occurs in a fluorescent light bulb, and light shining on a substance that glows which occurs in the white phosphorous in the inside of the fluorescent tubes
Continuous Spectrum
all the colors of white light when viewed through a spectroscope, ROYGBIV
Bright Line Spectra
distinct lines of color (wavelength) given off an element when viewed through a microscope
Color of Objects
the color we see due to the wavelengths reflected. Blue objects reflect blue wavelengths and red objects reflect red wavelengths, etc. Black objects absorb light and white objects reflect all wavelengths
Primary Colors
when mixed they produce white: blue, green, and red
Primary Pigments
yellow, cyan, magenta
Luminous Objects
give off their own light, example: sun, light bulb, candle flame
Illuminated Objects
reflect light, everything we see that isn't luminous
Luminous Intensity
brightness of the source, measured in candles or candle power
Luminous flux
brightness of the source, more commonly used than luminous intensity, measured in lumens
Illumincance (Illumination)
the amount of light that falls on a surface, depends upon the brightness of the source and how far the surface is from the source
Illuminance Calulation
1m/m^2
Transparent Objects
allow light to pass through without distortion, example: clear glass or air
Translucent Objects
allow light to pass through but the light is distorted, example: frosted glass
Opaque Objects
do not allow light to pass through, example: solid wall
Reflection of Light
light rays will bounce off a surface at the same angle they struck
Law of Reflection
angle of incidence = angle of reflection
Diffuse Reflection
reflection off a rough surface, no image is seen
Regular Reflection
reflection off a smooth surface like mirrors, images are seen
Dispersion
breaking of white light into its colors when it passes through a prism, it produces a continuous spectrum (ROYGBIV)
Rainbow in the Sky
produced when tiny water droplets in the sky act as prisms and disperse the light
Real Image
can be projected onto a screen and is always upside down if the object is right side up. Image distance is positive, magnification and height are negative
Virtual Image
cannot be projected and is only seen on the mirror or lens, they are always right side up. Image distance is negative, magnification and height are positive
Refraction of Light
as light passes from one medium to another, it changes velocity. If the light enters the new medium at an angle, the light ray will bend. The degree to which it bends upon the optical densities of the media involved
Law of Refractions
as light pases from less dense medium into more dense medium, it will blend towards to the normal. If the light ray passes from more dense to less dense, it bends away from the normal
Index of Refraction
numerical value for the optical density of the substance
Total Internal Refraction
when a light passes from more dense medium toward less dense medium, if the angle is large enough, it wil not refract out of the substance but rather reflects inward
Dual Nature of Light
light has the properties of both particles and waves
Photo Electric Theory
when light strikes a thin foil, electrons are emmitted off the backside of the foil as if a collision took place, this effect could not be explained by the wave theory and was a conclusive support for the particle theory
Concave Mirrors
curved inward
Convex Mirrors
focal length is negative
Flashlights and spotlihts
they contain a concave or spherical mirror or parabolic mirror, the light source is placed at the focal point and the light shines back on the mirror and reflects as a beam
Converging (convex) lens
thicker in the middle and thinner on the ends, example: magnifying glass
Diverging (concave) lens
thinner in the middle and thicker on the ends
Compound lens system
(microscope or telescope) contains at least 2 lenses, the real image is produced by the first lens (objective lens) becomes the object for the second lens (the eyepiece) that magnifies it as a larger virtual image
Human Eye
contains a flexible converging lens surrounded by muscles, the muscles contract to focus near and relax to focus far, a real image is focused on the black of the eye (retina)
Nearsightedness (myopia)
the lens can focus near but not far, most young people who need glasses are nearsighted, corrected with a diverging lens
Farsightedness (hyperopia)
the lens canot focus near, almost all people become this as they age and need reading glasses, converted with a converging lens
Mirage
change in density above road is caused by heat, causes the light to bend and never reach the road
Sun not where it appears?
light left sun 8 minutes ago, the light is going to the atmosphere, different in n's and the light bends. The light bends from vacuum to air, the n changes
Scattering (blue sky)
blue wavelengths reflect off air molecules and scatter in all directions