Ground state?
When an electron or atom is in its lowest possible energy state. Known as the most stable state.
Activated (excited) state?
When an electron or atom is in a higher energy state than its ground state. Known as unstable.
Quantum?
A specific (indivisible) amount - usually of energy. Plural: quanta.
Photon?
A “parcel” of light with a quantum of energy.
What are the wavelength ranges for ultraviolet, visible and infrared light?
Ultraviolet: < 400 nm
Visible: 400 - 700 nm
Infrared: > 700 nm
Absorption Spectra?
Is formed when light passes through a gas and is then refracted by a prism.
The Photoelectric Effect?
The ejection of electrons from a metal when light above a certain minimum frequency shines on it. This effect is proof that light has a particle nature too because it can be understood as a stream of photons.
Work Function?
The minimum amount of energy needed to emit an electron from the surface of a metal. Symbol: W0
Threshold (cut-off) frequency?
The minimum frequency of incident radiation at which electrons will be emitted from a particular metal. Symbol: F0.
Photo-cell?
An electric cell that produces current when light falls on it. A well known application of photo-cells is to produce solar electricity using sunlight.
What are the two things that light can behave as?
Light can behave both as a wave or a particle.
What is light defined to be?
Light is defined as a wave. It undergoes reflection; as in light being reflected off a mirror. It undergoes refraction; as in light slows down when it moves from air into water. It undergoes interference; as in how two beams of light can pass through each other and carry on as if nothing occurred. Lastly, it undergoes diffraction; as in light spreads out when it passes through a narrow slit.
Electronvolt, unit and conversion to Joules.
Is the unit of energy commonly used in photoelectric effect calculations. S.I. unit: eV
Conversion: 1eV = 1.6 x 10-¹⁹ J (same as the charge on an electron).
