Ahoujja Final
Interference
Superposition of two or more waves. Constructive interference occurs when the waves are in phase and therefore combine to form a larger wave; destructive interference occurs when the waves are out of phase and partially (or fully ) cancel each other
Penumbra
Partial Shadow created by blocking out only a portion of the light source
Photon
Particle of light (or other electromagnetic radiation) having an energy (hc/X, where h = 6.63 x 10^-34 Js is Planck's constant, c = 3 x 10^8 m/s is the speed of light, and X is the wavelength
Photographs taken on the moon's surface show a colorless sky. Explain Why.
Photographs taken on the moon's surface show a colorless sky because it has no atmosphere.
Antinode
Point of maximum amplitude due to constructive interference
Node
Point of minimum amplitude due to destructive interference waves
How do police officers use the Doppler effect to determine the speed of an automobile?
Police officers use the Doppler effect to determine the speed of the automobile by using a radar gun which shoots radio frequency waves off the car and then registers the change in frequency, the Doppler effect, to know the speed.
Linear Superposition
Two or more waves combine (interfere) without forming any byproducts
Explain why the colors are "reversed" in a secondary rainbow.
A secondary rainbow has its colors reversed because there are two reflections inside of each raindrop
How could you determine whether a certain green light has a single wavelength or a broad distribution of wavelengths?
One way to describe a certain color might be to show an intensity distribution curve.
Photosynthesis
Chemical process by which plants produce sugar from water and carbon dioxide by using sunlight
Frequency
Number of waves per second
Determine the speed of light in vegetable oil and diamond if their indices of refraction are 1.51 and 2.41 respectively.
3x10^8 m/s/speed of light in vegetable oil=1.51 a. Speed of light in Vegetable oil= 1.99x10^8 m/s 3x10^8/2.42=speed of light in a diamond a. Speed of light in a diamond=1.24x10^8 m/s
Describe and experiment that demonstrates the particle (photon nature of light.
5. The Photoelectric effect to explain that mass-less bundles of light energy are absorbed by atoms, called photons. If the light strikes a metal, electrons are emitted, but the effect will not occur if the frequency of the light it too low.
Standing Wave
An interference pattern formed by two waves of the same frequency moving in opposite directions; the pattern has alternative minima (nodes) and maxima (antinodes)
Magenta pigment + cyan pigment + yellow pigment =
Black Light
Magenta pigment + cyan pigment =
Blue Light
Pinhole Camera
Box with a pinhole capable of making a dim inverted image on a photographic film or screen
Doppler Effect
Change in the frequency of waves due to motion of the source, the observer, or both
Why are clouds white on a sunny day?
Clouds are white because the visible light scatters all colors equally for the most part. This non-selective scattering is responsible for the white appearance of clouds. When the sky is brighter, then the clouds have more visible light to scatter creating that whiter look.
Hue
Color name (e.g. red, yellow, green) that distinguishes one color from another
Umbra
Dense inner portion of a shadow where partial shadows overlap
Rainbow
Display of colors due to refraction in raindrops or other droplets of water
Wavelength
Distance between successive waves; the wavelength of light generally determines its color
Wavelength
Distance between wave maxima
Three projectors are adjusted to produce white light on a screen. If you stand in front of the red projector, what color will your shadow be? If you stand in front of the green projector, what color will your shadow be? If you stand in front of the blue projector, what color will your shadow be?
If you stand in front of the red projector then the shadow is cyan. If you stand in front of the green projector then the shadow is magenta. If you stand in front of the blue projector then the color is yellow.
Infrared Waves (radiation)
Invisible electromagnetic radiation with wavelength slightly longer than red light; radiant heat waves
Wave Model of Light
Light consists of electromagnetic waves
Particle model of light
Light consists of photons or particles having energy hf
Lightnign strikes the ground one kilometer away (a) How long does it take the light to reach us? (b) How long does it take the sound (thunder) to reach us?
Light: 1000m/3x10^8 m/s= 3.33x10^-6s Sound: 1000m/343m/s=2.91s
Amplitude
Maximum Displacement from equilibrium in a wave
Saturation
Purity of color (similar to "chroma" or "color intensity")
Index of Refraction
Ratio of the speed of light in air to the speed in the medium
Which travels faster in glass: red light or blue light? Which travels faster in water?
Red Light travels faster through glass than blue light. Red light also travels faster in water than blue light.
Determine the frequencies of red light (X = 650 nm) and blue light (X = 460 nm)
Red Light=3x10^8 m/s/650nm=4.62x10^14 Hz, Blue Light=3x10^8 m/s/460nm=6.5x10^14 Hz
Rayleigh Scattering
Selective scattering of light by small particles; makes the sky appear blue and the setting sun red
Brightness
Sensation of overall light intensity, ranging from dark, through dim, to bright
Why is the sky blue and the setting sun red?
The blue color of the sky is due to scattering of sunlight by molecules of air. blue light is scattered much more efficiently than light with longer wavelengths, so it appears brighter. The suns sets red because the blue light has been removed by scattering. The further the light has through the atmosphere, the more blue is scattered making the sunset more red
Chlorophyll
The material in leaves that strongly reflects green light
Describe the pitch of a train whistle as it approaches, passes by, and continues on its way.
The pitch of a train whistle as it approaches, passes by, and continues is shown by the Doppler Effect. As the train approaches the frequency of the whistle sound increases until it passes by. When it passes by the whistle sound's frequency is at its peak. After is passes by is continues the frequency of the train whistle sound decreases until it is unable to be heard.
Under what conditions would the shadow of a ball on a screen have no umbra?
The shadow of a ball will have no umbra if the ball is completely surrounded by light
A spotlight produces a shadow of a ball on a wall. What happens to the size of the umbra as the ball is moved farther away from the light?
The size of the umbra gets smaller as the ball is moved farther away from the light.
What is the range of wavelengths in the visible spectrum expressed in nanometers and expressed in meters?
The wavelengths in the visible spectrum expressed in nanometers is 400nm to 700nm. In meters it is 0.00000040m to 0.00000070m
Additive Primaries
Three Colors of light (generally red, green, and blue) that can be mixed together to obtain any other desired color
Subtractive Primaries
Three colors of filters or pigments that can be combined to produce other colors (including black) by absorption; examples are yellow, magenta, and cyan or red, yellow, and blue
Hertz
Unit of Frequency; equals one wave per second
Dispersion
Variation in the speed of a wave with frequency (or wavelength). The spreading of light into a spectrum of different colors.
Yellow light + magenta light =
White light
Light Ray
a line that represents the path of light in a given direction
Partitive Mixing
additive color mixing by placing separate sources very close to each other
Which of the following determines the speed of a wave? a) wavelength b) amplitude c) frequency d) medium through which it travels
d) medium through which it travels
Green light + magenta light =
white light
Yellow light + blue light =
white light
Determine the wavelength of radio waves transmitted by an FM radio station having a frequency of 89.5 MHz (1 MHz = 10^6 Hz)
x=3x10^8 m/s/89.5 MHz= 3.35 m
Red light + green light =
yellow light
