electron microscopes
DESCRIPTION
Electron Microscopes. 27-7. Developed in the 1950s Two Dimensional Image Electrons are accelerated by a Voltage of 10 5 V These Electrons have a wavelength of about .004nm Practical resolution is .1 to .5nm This is still 10 3 better than visible light 400-800nm. - PowerPoint PPT PresentationTRANSCRIPT
Electron Microscopes27-7
Tran
smiss
ion
Elec
tron
Micr
osco
pe
Developed in the 1950s
Two Dimensional Image
Electrons are accelerated by a Voltage of 105V These Electrons have
a wavelength of about .004nm
Practical resolution is .1 to .5nm This is still 103 better
than visible light 400-800nm
Elec
tron
Micr
osco
pe
Elec
tron
Micr
osco
pe
Scan
ning
Ele
ctro
n M
icros
cope
Resolutions to 1nm Produce 3D image 1st commercial
product 1965
Scan
ning
Ele
ctro
n M
icros
cope
Scan
ning
Ele
ctro
n M
icros
cope
Scan
ning
Ele
ctro
n M
icros
cope
Scan
ning
Tunn
elin
g EM
Developed in the 1980s
.1nm resolution laterally
.01nm resolution vertically
Uses Quantum Tunneling 30-12
Scan
ning
- Tu
nnel
ing
Scan
ning
- Tu
nnel
ing
Atomic Spectra27-11
Atom
ic Sp
ectra
Bohr
Mod
el
Bohr Model relates the jump down between excited states of the atom to the energy of a photon
Each line of the spectrum is a photon step
The larger the step, the more energy the photon Therefore the shorter
the wavelength And higher frequency
Emiss
ion
Spec
trum
Abso
rbtio
n Sp
ectru
m
Hydr
ogen
Ser
ies
Rydberg Constant R = 1.0974 x 107m-1
Balmer Series
Lyman Series
Paschen Series
2^1
2^211
nR
2^1
2^111
nR
2^1
2^311
nR