(2.2) - Electromagnetic Radiation and Quantum Phenomena Flashcards
Threshold frequency
The minimum frequency needed to eject an electron from surface of a material. If f>f0, electrons are emitted, but if f<f0, photons are not emitted due to 1 to 1 interaction
Work function ϕ
Minimum energy needed to eject an electron from the surface of a material
Stopping potential
Minimum voltage needed to stop the most energetic photoelectrons ejected from a material’s surface
Electronvolt
Work done or kinetic energy gained to accelerate an electron through an electric potential difference of 1 volt
What does increasing the intensity of radiation do in photoelectric affect?
- More photons emitted per second
- If f>f0, more electrons are emitted per second
Ionisation
Atoms loses or gains electrons
Excitation
Atomic electron absorbs energy, moves up energy level
De-excitation
Excited atomic electron emits energy, moves down energy level
How do Fluorescent tubes produce visible light
- Electrons from cathode collide with mercury atomic electrons, exciting them, then they de-excite, producing UV
- UV photons collide with phosphor atomic electrons, exciting them, then they de-excite, produce VL
Line Spectra
Excited atoms emit wavelengths of certain colors
What is it and how is it represented
Emmision spectra
- A spectrum of light emitted by a substance when its atoms move from high energy to low energy state
- It is represented with colored lines on a black background
What is it and how is it represented
Absorption spectra
- Substance absorbs some frequencies of light depending on if the energy matches the energy need to move electrons up in energy level
- It is represented by black lines on a colored background
Electron diffraction suggests light is a wave or a particle?
Wave
The photoelectric effect suggests light is a wave or a particle?
Particle
Diffraction
Waves pass through a gap or around an obstacle and the waves spread out
Effect of momentum on diffraction
Higher momentum = Lower wavelength
Less wavelength = Less diffraction
How must changes of knowledge need to be evaluated?
- Peer review
- Validation by the scientific community
Equation for photoelectrons per second
maximum current / charge on electron
