electron microscopes

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