SPANGLER SCIENCE

LIGHT

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LIGHT NOTES


ELECTROMAGNETIC SPECTRUM:

*range of ElectroMagnetic waves placed in order by decreasing wavelengths. (ripples on water)

*Wave- anything that causes a disturbance and transmits energy thru matter or space.(light, sound, seismic)

-way energy is carried away from source.

-transfers energy as vibration occurs.

-as wave travels-energy causes matter to move.

-medium- substance that wave travels through.

*EM waves are a form of energy that travels through space or matter. 

ie: sunlight to earth

*Frequency- (# of waves in set time) decides energy.

-short wavelengths & high frequency= high energy

-long wavelengths & low frequency= low energy

- includes radio, microwave, infrared, visible light, ultraviolet light, 

x-ray, & gamma rays.

*CSS 6a:   Light is part of the EM spectrum


LIGHT: 

*Visible light is narror range within the EM spectrum

-only waves we can see from the EM spectrum, rest invisible.

-made from colors (ROY G BIV), different wavelengths of light.

-longest wavelength-red; longest-violet, most energy.

-wavelengths affect the eye differently so we see different colors.

*Color- decided by absorbtion from object.

objects absorb color (hide) & reflect others (see)

-color seen is color reflected off object.

-reflect all color-white// absorb all color-black

-sunlight- mixture of colors

fyi: ozone layer- sunlight on oxygen molecules.

*White Light- when all colors are mixed.  

-visible light of all wavelengths of color combined.

-light enters and sent to retina (eye); 3 cones; red, blue, green; 

all colors are absorbed of visible light-see white.

Eye (human’s) can distinguish millions of colors & hues.

-Prisms: white light in, color out due to bend of light by prism.

seperates white light into parts.

*CSS 6e:   White light is a mixture of many wavelengths, how the eye sees it

Prentice Hall EM wave site


1. REFLECTION:   (bounces off)

*light hits an object that it can’t enter and so bounces off.

ie: mirror, sunglasses. 

1.1. Regular reflection- same angles due to smooth surface.

ie: mirror.    Always equal.

1.1a. Angle of incidence- incoming rays and imaginary line perpendicular to surface.  

1.1b. Angle of reflection- reflected ray from light wave and imaginary line

1.2. Diffused reflection- rays scatter due to uneven or bumpy surface. 

*we see most objects because of scattering.


2.TRANSMISSION OF LIGHT:    (passes thru)

* Light usually travels in a straight line unless medium changes/bends it.      In rays away from source. 

*passing of light through matter (things that take up space-8CSS)

-opaque-no light thru   ie: wall

-transparant-all light thru   ie: glass

-translucent- some light thru   ie: wax paper

*REFRACTION= change in speed & direction.

-when passing from one material to another it will change speed and  angle.  

-travels more slowly through certain medium (atoms-like diffusion)  

  ie:  light travels faster in air than water

*light bends when changes from one medium to another.

-changes direction when interacts with matter.

-bend depends on wavelenghts (shorter-more bend).

-bend of light due to change of speed.

-light refracts once hits lens in eye; to retina. (camera)

* only see when light waves bounce off object, reflected or scattered, and into eyes.

-medium not needed for light to move, part of EM Wave.


3. ABSORPTION/SCATTERING:

ABSORPTION-   (enters)

* light absorbed by the material/medium that takes in the light holds it.

* transfer of energy by light waves to particles in matter.

ie: dark material and pavement.

black t-shirt in summer- hot due to holding light energy.

*light weakens as further from source- more matter absorbs it.

-objects closer to the light are brighter than distant objects.

-air particles absorb some light so gets dim the further away.

SCATTERING-  (released)

*the  release of light energy by matter that absorbed extra energy.

*material decides what happens.

*light scatters in all directions once released.

ie: can see outside of beam from flashlight.

ie: sunlight throughout air.

sky is blue because blue is shorter wavelength and scattered more.

LENSES

Lenses-  bends light rays

* Convex lens- thick middle and thin on edges

-bends parallel lines of light to focal point.

-surface highly curved

-converging lens

-image larger and right-side up.

ie: eye, microscope, magnifying glass

*Concave- thick outside and thin in middle

-spreads out parallel lines of light.  no focus

-diverging lens

-image smaller and upright.

ie: glases to correct far-away vision.


* CSS 6b:  For light to be seen, scattered light must enter the eye.

*CSS 6c:  Light travels in straight lines except       when the thing it travels through changes it.

*CSS 6d:  How simple lenses work in the eye.

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