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)