CH 8, 11 and 12 Reading

Chapter 8

8.1.1 Photons Carry Energy

  • Light is composed of many particles of light called photons

  • A photon is a particle that has only kinetic energy

    • Its potential Energy is 0

    • Its never at rest

  • Atoms can gain energy by absorbing a photon

  • Atoms can lose energy by emitting a photon

  • Photons have momentum

    • E2=(pc)2E² = (pc)²

    • Magnitude of momentum of a photon whose energy is EE is p=E/cp=E/c

8.1.2 The Electromagnetic Spectrum

    

  • Only photons whose energies fall between about 1.8 eV (red light) and 3.1 eV (violet light) can be detected by human eyes

Checkpoint 8.1-C-01

  • The intensity of sunlight above the Earth’s atmosphere is about 1400 W(J/s) per square meter. That is, when sunlight his perpendicular to a square meter of area, about 1400 W of energy can be absorbed. Using the photon energy of green light, about how many photons per second strike an area of one square meter?

  • p=1400W(J/s)p = 1400 W(J/s)

  • Green light = 2.5 eV

8.2 Electronic Energy Levels