Matter, Light, and Energy Flashcards
Explain Rutherford experiment
Shot positive alpha particles at gold foil and noted how occasionally they bounced backwards. Discovered most of atom was empty and dense positive core(nucleus)
What does number of protons in atom determine?
Which element it is
What did Planck and Einstein show about electrons in atoms?
Can only occupy at specific energies i.e energies are quantized
What happens if you add enough energy to electron?
It leaves atom altogether and atom is ionised. Ion left with net positive charge
What happens if electron with low enough energy wanders by ion?
Can be captured and become neutral again. Called recombining
What happens when an electron moves from higher level to lower level?
Loses energy and releases photon
Range of visible wavelengths
4x10^-7 m (violet) to 8x10^-7m (red)
What is the photoelectric effect?
Light can knock out electrons evidence for being a particle
What is luminosity?
•energy per second emitted in photons
•intrinsic property of the object
What is Flux?
•energy in photons passing through a given area per second
•measurable (apparent) property
What is a spectrum?
The flux of photons at each wavelength
What most matter be to thermalise photons and atoms?
Opaque
What is a black body spectrum?
The spectrum arising from thermal emission.
Peak wavelength scales inversely with temperature
Explain emission spectra
Photon energies correspond to difference in energy levels for that particular atom. Hence photons emitted at specific wavelengths for each atom
Explain absorption spectrum
Photon of precisely right energy hits electron, electron jumps to higher level swallowing photon and photon then missing from light
