Y1 Ch 04 Particles of Light Flashcards
The photoelectric effect
This is seen when a gold leaf electroscope is not discharged by white light no matter how long the light shines on it. This contradicts the theory that light is a wave. However, UV light discharges it immediately. This supports the theory that light travels as a particle.
Threshold frequency
The minimum frequency of light required to cause the photoelectric effect.
Intensity
The rate of energy transfer per unit area.
Photoelectron
an electron emitted during the photoelectron effect
Planck’s formula
E = hf
Threshold energy
The minimum amount of energy required to cause the photoelectric effect.
Potential well
A model to help us understand why electrons require energy to remove them from a metal. An electron has at least potential energy in the potential well.
Work Function
The least energy needed to release a photoelectron from a material. This equals the threshold frequency.
Transition of energy
hf = work function + 1/2 mv^2
Semiconductor
A material with conductivity between a metal and an insulator.
Stopping Potential
when the opposite electrode is negatively charged so the photoelectrons turn around so they don’t reach the negatively charged particle.
Wavelength of particles
p = mc
de Broglie wavelength
wavelength = h/mv
Wave-Particle Duality
The idea that matter and radiation can be described best by sometimes using a wave model and sometimes using a particle model.
