Electromagnetic Radiation and Quantum Phenomena Flashcards
What is the Photoelectric Effect?
When light hits a metal’s surface, it is bombarded by photons. If one of these photons collide with a free electron, the bonds holding it to the metal break and the electron is released.
What are the conclusions of the Photoelectric Effect?
- no photoelectrons are emitted if the radiation has a frequency below a certain value.
- photoelectrons are emitted with a variety of kinetic energies
- the number of photoelectrons is proportional to the intensity of the radiation.
What is Threshold Frequency?
The minimum frequency of incident electromagnetic radiation required to remove a photoelectron from the surface of a metal.
What are the Assumptions of the Wave Theory of Light?
- energy carried is proportional to the intensity
- the energy carried by the light would be spread evenly over the wavefront
- Each free electron would gain a bit of energy from each incoming wave.
meaning eventually each electron would gain enough energy to leave the metal.
What is the equation for photon energy?
E=hf
How did Einstein model light?
-He suggested that light can only exist in discrete packets. (photons)
-photons of light have one-to-one, particle-like interaction with an electron, transferring all its energy to that one specific electron only.
What is the Work Function?
the energy needed to break the bonds holding the electron down
what is the equation for work function?
work function = threshold frequency x h
what is the equation for maximum kinetic energy?
Ekmax = hf - work function
Why is the kineti energy of the electron independent to intensity?
they can only absorb one photon at a time
What is n=1?
ground state
What is the electronvolt?
- 1 eV in Joules?
the kinetic energy carried by an electron after it has bee accelerated through a potential difference of 1 volt.
- 1.6 x 10^-19 J
How do Fluorescent tubes use excited electrons to produce light?
- Fluorescent tubes contain a mercury vapour, across which a high voltage is applied. When electrons collide with the fast moving free electrons, they’re excited to a higher energy level. When these excited electrons return to their ground states, they emit photons in the UV range. A phosphorus coating on the inside of the tube absorbs these photons, exciting its electrons to higher energy levels. Once these electrons de-excite, they emit lower energy photons in the visible light range.
What happens when you split light from fluorescent tubes with a prism or diffraction grating?
Line Emission Spectra
How is the line spectrum seen?
- What does each line represent?
-seen as bright lines against a black background.
- each line is a particular wavelength of light emitted.
