Exam 4

Question 1

LASER

Answer 1

Light
Amplification by
Stimulated
Emission of
Radiation

Question 2

How a laser works:

Answer 2

1. excitation - energy is added to promote electrons to higher orbitals.
2. emission - electrons returns to lower energy source.
3. stimulated emotion - causes a photon to be released.

Question 3

Advantages of Lasers

Answer 3

• high energy
• polarized
• coherent
• narrow bandwidth

Question 4

Types of Lasers

Answer 4

1. solid state
2. gas
3. dye
4. semiconducting diode

Question 5

Advantage and Disadvantage of semiconducting diode

Answer 5

+ small in size, cheap

- wavelength dependent on band gap

Question 6

Population inversion

Answer 6

more electrons in higher energy state, than in lower energy state; necessary for a laser.

Question 7

Examples of Lasers

Answer 7

YAG, Ruby

Question 8

Order of Radiation from shortest wavlength to longest

Answer 8

gamma -> Xray -> UV -> infrared -> microwave -> radio

Question 9

Analytical Applications of Lasers

Answer 9

• laser induced fluorescence
• raman scattering
• MALDI-TOF
• doppler effect
• CRD spectroscopy

Question 10

Advantages of making instruments as small as possible

Answer 10

• saves lab space; makes room for more instruments

- portable; can use instruments in the field which leads to reduction of time spent in lab and cost

Question 11

Disadvantages of making instruments as small as possible

Answer 11

short lifespan; which can impact reproducibility

Question 12

Automation

Answer 12

reduces the amount of time needed for an analyst to go thru a number of samples

Question 13

Can everything be automated?

Answer 13

NO

Question 14

If it is a repetitive task….

Answer 14

it can be automated.

Question 15

What are nanoparticle properties based on?

Answer 15

• composition
• size
• shape

Question 16

Low angle light scattering

Answer 16

use laser to blast something and have light diffract off it; particle size is determined based off of light defraction

Question 17

What is low angle light scattering used for?

Answer 17

to determine particle size

Question 18

Brownian motion

Answer 18

particles move around in solution; causes an issue when viewing scatter of a laser

Question 19

How do you view particles when they are moving?

Answer 19

• CCD cameras

- Photon counters

Question 20

Dynamic light scattering

Answer 20

“photon correlation spectroscopy”

- uses doppler broadening of raliegh scattered light as result of brownian motion

Question 21

Photosedimentation

Answer 21

measures the rate at which particles settle throughout a liquid; larger particles settle faster than smaller particles

Question 22

5 Assumption of Photosedimentation

Answer 22

1. particle must be smooth, spherical
2. the final velocity of the particle must be reached instantly
3. all particles have same density
4. all particles are assumed to move independently
5. the fluid behaves as a continuum with a constant viscosity

Question 23

Will all the stuff in water fall out of solution?

Answer 23

NO, not all stuff in water will fall out of solution.