Particle Properties of Light

1
Particle Properties of Light

• There are certain properties of light that cannot
  be explained using the wave model.
• Blackbody radiation
• emission of light from hot objects
• example electric stove burner
• wavelength of radiation depends on the
  temperature
• Max Planck (1900) energy can either
  be released or absorbed by atoms in
  discrete chunks.

2

• Since energy can only be released in specific
  amounts, we say that the allowed energies are
  quantized.
• Quantum smallest amount of energy that can be
  emitted or absorbed as electromagnetic radiation
• Planck developed an equation to determine the
  energy of a single quantum.
• E h?
• Plancks constant (h) 6.63 x 10-34 J s.

3
Photoelectric effect

• studied by Albert Einstein
• the emission of electrons from a metal when light
  shines on the metal
• Only certain frequencies of light caused
  the effect.

4

• Another way to think of a beam of light through
  space is as a stream of tiny packets of energy.
• He called these packets of light photons.
• That is, electromagnetic radiation can sometimes
  have properties that are characteristic of
  particles.
• Different wavelengths of electromagnetic
  radiation produce photons of different amounts of
  energy.
• The energy of the photons of electromagnetic
  radiation is directly related to its frequency
  and inversely related to its wavelength.

5

• Example
• Red light has a wavelength of 700 nm and blue
  light has a wavelength 480 nm.
• Photons of red light have a smaller frequency
  than blue light.
• Therefore, photons of red light have less energy
  than photons of blue light.

6

• Sample Problem
• Determine the energy of a photon whose frequency
  is 5.09 x 1014 Hz.

7

• Is light a wave or does it consist of particles?
• Light possess both wavelike and particle-like
  characteristics , and depending on the situation,
  will behave more like a wave or more like a
  particle.
• Since light can consist as a wave or a
  stream of particles, we say that light has
  wave-particle duality.

8
Outcome Sentences

• After reflecting on todays lesson, complete two
  of the sentence starters on your notes for today.

• Sentence Starters
• Ive learned
• I was surprised
• Im beginning to wonder
• I would conclude
• I now realize that