CHAPTER 14 LIGHT AND COLOR

We need to mash together what we know about electricity magnetism When electric fields and magnetic fields vibrates Electromagnetic Waves . Electric fields change by changing magnets Magnetic fields change by changing electric currents All electromagnetic waves in a vacuum TRAVEL AT THE SAME SPEED …. 300,000 KM/S 186, 000 MI/S

Why can you see through some materials (TRANSPARENT ) while other materials you can’t see through( OPAQUE)? When light hits a material , electrons within materials atoms are stimulated to VIBRATE If the VIBRATIONS are LARGE and LONG LASTING the energy is absorbed and the material appears opaque to that frequency. LIGHT CAN BE ABSORB OR REFLECTED DEPENDING ON SURFACE TYPE

If the VIBRATIONS are SMALL and SHORT LIVED the energy is remitted and the material appears transparent There is a time delay between absorption and reemission – DIFFERENT MATERIALS ALLOW LIGHT THROUGH AT DIFFERENT SPEEDS glass 2/3 the speed of light water is ¾ the speed of light Glass can be made to be transparent to a variety of ELECTROMAGNETIC MATERIALS

Glass is …. transparent to VISIBLE LIGHT opaque to INFARED LIGHT opaque to ULTRAVIOLET LIGHT

Color Science Visible light color differs according to frequency

Highest Frequency Light we can detect is VIOLET and the Lowest Frequency Light we can detect is READ The pneumonic device to remember the order of colors ROY GEE BIV Red Orange Yellow Green Blue Indigo Violet

White is the mixture of all light together Black is the absence of light Colors we see are the frequency of light the object REFLECTS BACK TO US Transparent objects appear the color they transmit Fluorescent Lamps have more BLUE AND VIOLET Incandescent Lamps have more RED AND ORANGE Sun Light more GREEN and RED

WHITE OBJECTS REFLECT BACK ALL COLORS OF LIGHT AND TEND TO BE COOLER IN TEMPERATURE THE DARKER COLOR AN OBJECT THE MORE ENERGY IT TENDS TO ABSORB AND THE WARMER IT TENDS TO BE

MIXING OF COLORS THE SUN TENDS TO BE MOST INTENSE IN THE YELLOW –GREEN WAVELENGTH THAT IS WHAT PLANTS TEND TO ABSORB MOST AND OUR EYES SEE BEST RED GREEN BLUE ARE THE PRIMARY COLORS – TOGETHER THEY MAKE WHITE

SECONDARY COLORS – TWO PRIMARY COLORS RED + GREEN = YELLOW RED + BLUE = MAGENTA GREEN + BLUE = CYAN COMPLEMENTARY COLORS – ANY TWO COLORS THAT MAKE WHITE MAGENTA + GREEN YELLOW + BLUE CYAN + RED

Why is the Sky Blue ? Light from the sun is absorbed by the Nitrogen (78% ) and Oxygen (21%) atoms in the atmosphere and reemitted( scattered ) in all directions The highest frequency light( violet and blue ) are scattered the most , our eyes are not as sensitive to violet as they are to blue.

As the frequency of light decrease the amount it is reemitted also decreases- SO red is scattered the least. Water vapor/ Dust/ Smoke absorb other frequencies of light and reemit them causing a whitening in the sky. Larger particles or water droplets do not reemit light as much causing a darkening. Water has a faint cyan color and absorb red light

Why are sunsets Red? Light that is not absorbed by atmosphere goes right through( transmitted ) ROY are not scattered Noon sunlight travels through least amount of atmosphere – appears pale yellow Sunset and Sunrise travels through most atmosphere VB scattered out – RO make it through to us. Pollution makes sunset more colorful

Why are clouds white ? Water droplets that make clouds come in many sizes – the very smallest drops absorb and reemit violet light. As droplets get bigger the larger the wavelength of light they absorb and reemit. All colors scattered – makes white,