An Electromagnetic Wave Light An Electromagnetic Wave

Electromagnetic wave = a distrubance of the electrical and magnetic fields which transports energy

The disturbance is caused by A photon Photons are particles of light Photons are packets of energy

See p 235 Electric field vibrates perpendicular to magnetic field

Photons Emitted when an e- drops down to a lower energy level

Frequency of wave created depends on Amount of energy in photon High energy photon = high frequency light wave Speed of light constant in vacuum …so…. High frequency = short λ

Energy of Photon determined by: Amount of energy given off by the electron as it drops to lower energy level Energy differences between atomic energy levels differ depending on what electron shells they are

e- excited by absorbing Energy (can absorb photons)

Transmission of Light Opaque objects = don’t transmit only absorb or reflect Transparent objects = transmit in straight lines Scattering = molecules transmit in all directions

Opaque objects absorb some frequencies of light Photon absorbed e- jumps up energy level Unstable atom vibrates so much energy is converted To heat

Opaque objects reflect other wavelengths The color reflected is the color we see If all colors reflected we see White, all absorbed we see black

Transparent objects Light passes through in straight lines Light absorbed by electrons in 1st molecule then re-emitted on opposite side Light re-emitted is same frequency as what was absorbed Re-emitted light goes to next molecule ……….page 238

Glass transparent to all visible light But not transparent to UV UV is natural frequency of glass molecules Makes them resonate, converts light to heat

Scattering Absorb light and re-emit in all directions Small molecule scatter higher frequency N2 and O2 of air scatter violet & blue Larger particles scatter lower frequency Very large particles absorb light and are opaque

Why ….. Is the sky blue? Are clouds white? Are storm clouds gray?