LIGHT ENERGY LIGHT ENERGY radiant energy visible THEORIES

LIGHT ENERGY

LIGHT ENERGY - radiant energy; visible THEORIES a. Wave Theory (Christian Huygens) - light behaves like waves in the water. b. Particle Theory (Isaac Newton) - light consists of streams of tiny particles moving at great speed. c. Electromagnetic Theory (James Clark Maxwell) - light waves are partly electrical and partly magnetic in nature ( electro- magnetic waves).

d. Quantum Theory (Max Karl Earnst Ludwig Planck) - light consists of streams of particles of electromagnetic waves called quanta (plural of quantum) e. Photon Theory (Albert Einstein) - considered the quanta particles (quantum theory) as photons. Accepted theories : particle and wave v. Light are little particles of energy moving like waves.

SOURCES a. Natural ex: sun, fireflies (luciferin + Oxygen), angler fish b. Artificial – man made/controlled ex: electric bulb, flashlight

SPEED Light travels in straight lines. Speed – 300 000 km/s (gas) * 8 mins – 150 M km from the sun Light travels faster than sound. * You see lightning before you hear the thunder. Gas – fastest Liquid – faster Solid – fast

BEHAVIOR * Light behaves differently in different materials. *Transmitted/absorbed transparent materials – allow much light to pass through (clear glass, clear water)

*Reflected or Bent translucent materials – allow only a small amount of light to pass through (frosted glass and windows) Opaque – don’t allow light to pass through (wall, man, bag, etc. ) Shadow is formed when opaque objects block the path of light. The shape and size of shadows depend on the distance and position of the object from the source of light. Parts of a Shadow: Umbra – darker part Penumbra – lighter part

REFLECTION – bouncing of light when it strikes a surface. Kinds: 1. Normal – light strikes a very smooth surface - incident rays bounce off evenly, reflected rays are not scattered - virtual image (clear & sharp image) 2. Diffuse – light strikes rough surfaces - reflected rays are scattered - no image is formed * Rays/beams of light – light radiating from the source 2 kinds: a. Incident rays – strike the surface b. Reflected rays – bounce off

KINDS OF MIRROR (very good reflector of light) 1. Plane – clear and sharp reflection and gives virtual image 2. Concave – curved inward and gives larger view ex: searchlights, headlights, flashlights, cosmetic mirrors, driver’s rear mirror 3. Convex – curved outward and gives smaller view ex: car’s side mirrors, shopping centers

PLANE MIRROR

CONCAVE MIRROR

CONVEX MIRROR

When you see the water of the pool/river seems to be shallow, must you dive or dip immediately? Why?

REFRACTION – bending of light as it travels through transparent materials. * Light moves at different speeds at different materials. *Speed of light is slower or reduced in solid and liquid(denser) which causes it to bend. LASER –Light Amplification by Stimulated Emission of Radiation.

REFRACTION The bending of a ray of light as it passes from one medium to another is called refraction.

Reflection and Refraction at an Interface

COLORS * White light (sunlight) is a mixture of colors and is refracted and separated by a prism. *Visible Spectrum -band of colors(ROYGBIV ) Red – longest wavelength and is bent the least Violet – shortest wavelength and is bent the most *The color you see in the object is the color that is not absorbed by the object, thus reflected. Ex: banana- all colors are absorbed except yellow (reflected) * White – all colors are reflected * Black – all colors are absorbed