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Ligh t Chapter 16

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Light. Chapter 16. Mission. In this presentation, we will do the following: define light. tell how light is measured. tell how light travels. explain the electromagnetic spectrum. tell how light is transferred. tell how colors are formed. - PowerPoint PPT Presentation

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Light

Chapter 16

Mission

In this presentation, we will do the following:

define light. tell how light is measured. tell how light travels. explain the electromagnetic spectrum. tell how light is transferred. tell how colors are formed. tell some applications of light in industry

and everyday life.

16.1 Light Fundamentals

Light - EM wave (transverse) that human eye can see.

Different light wavelengths are seen as different colors.

Ray - straight line representing path of beam of light.

Ray optics - ray diagrams to study travel of light.

EM Spectrum

The electromagnetic spectrum includes, from longest to shortest:

radio waves microwaves infrared Visible light ultraviolet X-rays gamma-rays

Transference of Light

Can be reflected, absorbed, refracted, transmitted.

To be black, all wavelengths of light hitting that object are absorbed; no light is reflected.

Solid objects, for the most part, will reflect light.

Transparent objects will transmit light through them.

The Speed of Light Galileo - 1st to say that light

had finite speed Ole Roemer - 1st to take data

from which speed of light could be measured

A. A. Michelson - 1st American to win Nobel prize measured speed of light

Use of laser allows for new way of measuring speed of light.

Speed of light, c, is 299,792,458 m/s or c = 3.00E8 m/s

Prac Pr 376

Sources of Light Luminous - emits light

Ex: sun, incandescent light bulb. Illuminated - reflects light

Ex: moon Luminous flux, P - rate at which

light is emitted. Unit is lumen, lm

Illuminance, E - illumination of a surface.

Measurement of light depends on sensitivity of eye.

Candela, cd - measure of luminous intensity which is luminous flux that falls on 1 sq meter of sphere with one meter in radius.

Inverse Square 379 Ex Prob 380 Prac Pr 381

Inverse Square – varies inversely as square of its distance from a light source.

Fig 16-6 379 Ex Prob 380 Prac Pr 381

16.2 Light and Matter Transparent - transmit light

waves Translucent - transmit light

waves but objects cannot be seen clearly.

Opaque - absorb or reflect light waves

How We See Light enters pupil

& travels through lens.

Image is focused inverted (upside down) on retina.

Image is transferred to brain by optic nerve.

Color Red to violet Spectrum - produced when

white light is passed through spectrum.

Primary colors - red, green, & blue

Secondary - magenta, cyan, & yellow

Complementary color - light of color & its complement add to produce white.

Dye - molecule that absorbs certain wavelengths & to transmit or reflect others.

Pigment - larger than molecule.

Mix to form suspensions rather than solutions.

White light can be formed by adding together primary light colors, red, blue, & green.

Subtractive primary colors, cyan, magenta, & yellow, are used in pigments & dyes to produce wide variety of colors.

Colors in soap & oil films are caused by interference of specific colors of light reflected from front & back surfaces of thin film.

Light is polarized if only waves vibrating in particular plane are present.

Fig 16-14 and 15 387 Light is polarized by scattering in air.

Ray & wave models of light – Particle-Wave Duality of Light

Conclusion Light is a transverse wave that

can be reflected, refracted, diffracted, transmitted, or absorbed.

Light travels through a vacuum. Speed of light (c) is 3.00 x 108 m/s Colors are produced additive or

subtractive processes.

Works Cited Physics: Principles & Problems, Glencoe http://hyperphysics.phy-astr.gsu.edu/

hbase/forces/isq.html http://acept.asu.edu/PiN/rdg/color/color.shtml http://sln.fi.edu/color/color.html http://imagers.gsfc.nasa.gov/ems/

waves3.html. http://www.glenbrook.k12.il.us/gbssci/

phys/Class/waves/u10l1c.html http://

www.kettering.edu/~drussell/Demos/waves/wavemotion.html

http://www.physicsclassroom.com/mmedia/optics/lr.html

Transverse Wave

Inverse Square Law

Color Addition

Reflection of Light

Thin Film

Thin Film Interference

Polarizers

Polarizers

Polarizers

Scattering

Scattering