Quantum Physics Flashcards
(19 cards)
Electron volt
It is an alternate unit of energy. It is defined as the amount of KE gained by an electron if it accelerates from rest through a p.diff of 1 volt
Energy of a photon
A packet or a quantum of electromagnetic radiation possessing a fixed amount of energy
Photoelectric emission
The emission of electrons when the surface of a metal is exposed to Light/Electromagnetic radiation
Work function energy
Energy required to bring electrons to the surface of the metal
Threshold frequency
The minimum frequency required to bring electrons to the surface
Why do emitted electrons have a range of kinetic energies
Not all electrons are on the surface i.e those electrons which are embedded within the surface might have to use some of their energy to reach the surface before they can be emitted hence they will be emitted with kinetic energy less than the maximum value
The theory of photoelectric emission
When electromagnetic radiation of appropriate frequency is incident onto a metal surface one part of the energy is used up in overcoming the work function of the metal and the remaining energy is converted into kinetic energy of the emitted electrons
When are emissions observed?
If the incident frequency is greater than the threshold frequency
What happens if the intensity is increased keeping the frequency constant
If intensity is increased keeping the frequency constant more number of photons will reach the metal surface in a given time,hence more number of electrons will be released therefore photoelectric current increases
What is the significance/importance of Photoelectric emission
It provides us with evidence that electromagnetic radiations exhibit a dual nature i.e electromagnetic radiation exists both as waves as well as particles
How do we that electromagnetic radiations don’t only exhibit wave properties
We know this because if wave nature is used to explain the phenomenon of photoelectric effect than any frequency, even that less than threshold frequency if exposed for a sufficient amount of time would have caused photoelectric emission to occur
Which phenomenon exhibits that electromagnetic radiation has wave properties
Diffraction, Interference and Superposition
Which phenomenon exhibits that electromagnetic radiation has particle like properties
Photoelectric effect
How can the particulate nature of electrons be verified
By allowing electrons to strike a fluorescent screen. Bright spots of light are observed to be uniformly distributed on the screen which implies that kinetic energy of electrons is converted into light as electrons strike the fluorescent screen and since KE=1/2mv2 i.e kinetic energy is associated with mass this confirms the particulate nature of electrons
How can the wave nature of electrons be verified
By making electrons undergo diffraction
Excitation Energy
the energy required to move an electron from a lower energy level to a higher energy level
Ionisation energy
When an electron receives sufficient energy which enables it to escape completely from the attractive forces of the nucleus
Absorption spectral line
A line joining any two energy levels which represents the energy wavelength required to cause excitation of the electrons between those levels
Which spectral line produces the shortest wavelength of electromagnetic radiation
The spectral line with the largest energy change
🔺E=hc/lambda
