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Light
Light•All light is produced by excited atoms
Excited Atoms•Electrons in an energy level have a specific amount of energy
•If an electron absorbs energy, it is bumped into a higher energy level
•This produces an unstable or excited atom
Photons•Atoms do not like to be excited. •The electron will loose the extra
energy by giving off a photon, allowing it to fall back into its original energy level
•Light is produced•Photon – a packet of
energy released by an excited electron
Electromagnetic SpectrumAn arrangement of all
electromagnetic waves by decreasing wavelength and
therefore increasing frequency
Longest wavelength ROY – G – BIV shortest wavelength
RedOrangeYellowGreenBlueIndigoViolet
Behavior of Light•Light behaves like a waveThe wave theory of light explains most of the properties and behavior of light very well. However, it can no longer explain all the things we’ve observed about light.
•Light behaves like a particleHigh energy light will produce an electric current when it strikes a metal plate, while low energy will not. If light was a continuous wave, even the energy from the lowly “red” light would eventually be absorbed and cause some electron movement – this does not happen.
Light Strikes Matter….
3 Things Can Happen:
1.Light can be transmitted
2.Light can be absorbed
3.Light can be reflected
Light Can Be TransmittedLight passes through the substance it strikes
•Transparent – light passes through so you can see clearly – like window
•Translucent – Light passes through but it is scattered so you cannot see clearly – like wax paper
•Opaque – Light does not pass through – like construction paper
Light Can Be Absorbed
Light passes through a substance and stays there
Example: When light hits a red stop sign, the stop sign reflects
mostly red wavelengths and absorbs all other colors so we do
not see them
Light Can Be Reflected
Light strikes a substance and bounces back
Example: When light hits a red stop sign, the stop sign reflects mostly red wavelengths and absorbs all
other colors so we do not see them
ReflectionReflection –bouncing back of a wave
when it hits a surface it can’t pass through
–Regular Reflection – very little scattering; the image looks exactly like the object
–Diffuse Reflection – light is scattered in many different directions; if image is formed at all, it does not look like the object
Mirrors•Mirrors REFLECT light•Types of mirrors
»Plane – a flat surface »Concave – surface of mirror curves inward
»Convex – surface of the mirror caves outward
RefractionRefraction – the bending of waves as
they enter a different medium
•Some mediums cause light to bend more than others
•Prism – an object that forms a spectrum as light passes through it
Lenses•Lenses REFRACT light•Types of lenses
»Concave – thicker at the edges than at the center
»Convex – thicker at the center than at the edges
Optics•Optics is the science of controlling light
•Light can be controlled in 3 ways:1. Block it2. Reflect it3. Bend it
(Mediums, mirrors, and lenses are used in optics)