Exam 1 Part 1 Flashcards
Describe the wavelength, energy, and frequency of red light.
long wavelength
low energy
low frequency
Describe the wavelength and frequency of UV light.
Short wave length
high energy
high frequency
What is the Photoelectric effect?
When light hits the surface of metal, particles are ejected, and electrons are emitted
Where do the electrons come from in the Photoelectric effect?
They come from the metal which contains atoms -> electons
How much energy do electrons leave with in the Photoelectric effect?
It depends on the wavelength of the light
Do metals like to lose electrons and why?
No, it takes energy (lowers potential energy)
they only have a finite amount of energy
What is the relationship between E_light and wavelength?
E_light is inversely proportional to wavelength (1/lambda)
What is the relationship between E_light and frequency
E_light and frequency are directly proportional
What does v stand for?
frequency
What does lambda stand for?
wavelength
What is the relationship between E_light and intensity?
E_light and intensity are directly proportional
What is another word for intensity?
brightness
What does psi stand for?
work function (constant)
What does the atomic number tell you?
protons=electrons
Explain why the photoelectric effect SHOULD “work” if intensity is high enough?
Intensity is proportional to energy (E_light)
so it should have overcome the threshold
E_light> Psi
Explain why the photoelectric effect DOESNT ALWAYS “work” if intensity is high enough?
only get potential energy iff the frequency is greater than initial frequency
v>v_o
Explain the expectation that KE should increase with intensity.
Intensity is proportional to E_light and
KE_e-=E_light-
What is intensity represented by on a wave function graph?
amplitude (middle of the graph to ‘hump’
Is light one big wave or a bunch of small waves?
a bunch of small waves (photons)
What does the color of a light determine?
The wavelength
Describe the relationship between photons and brightness.
of photons increase
as brightness increases
#photons increases
What are photons?
The smallest ‘piece’ of light and the smallest unit of energy for a given wavelength
Explain the photoelectric effect in terms of photons.
The atom of the metal needs enough photons to get e- to leave
What does the variable h stand for?
planks constant
What does the variable c stand for?
the speed of light
What is the definition of brightness?
change in # of photons
What is absorption?
Electron in atom gains energy
What is emission?
Electron in atom releases energy
Is the system happier at ground state or excited state?
The system is happier at ground state because it has a lower energy (delta H)
In an energy level diagram, would a red light be the small energy level jump or the largest?
smallest because energy is inverse to wavelength
Describe the Bohr Model for H-atom?
tiny e- orbits massive proton
imposed quantized energy levels on electron in atom
leads to quantized orbital radii
predicts locations of spectral lines (lambda)
What does the constant l stand for?
angular momentum
Negative potential energy is ____.
Attraction
Positive potential energy is ____.
repulsion
In the Bohr Model: explain what happens to energy as n gets bigger.
As n gets bigger the energy gets closer to 0 and the energy level approaches infinity
True/False: In the Borh Model: To move infinitely far away, it take infinite energy.
False, It takes a finite amount of energy to move infinitely far away
Describe the ‘sign’ (+/-) of Energy at n=1 and what happens to it as n increases.
at n=1 Energy is the most negative and get less negative as n increases
energy approaches 0
What did the Bohr Model not explain?
Variation in spectral line intensity (brightness)
Change in spectra (color) in presence of magnetic field
Spectra of atoms with 2 or more electrons**
Explain the idea of light as it relates to Wave-Particle Duality.
It was classically thought of as a wave but now as a particle because it is individual photons
Explain the idea of matter as it relates to Wave-Particle Duality.
Matter can appear as both a particle and a wave (has both properties)
What does the constant p stand for?
momentum
Who suggested there was wavelength for particles?
DeBroglie
Explain the relationship between the size of things and their wavelength.
small things have noticeable wavelengths and large things do not
