Optical Phenomena Flashcards
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).
