Electromagnetic Radiation Flashcards
1
Q
The principles that govern the analytic techniques and instrumentations in the lab fall into four basic areas:
A
Spectrophotometry
Luminescence
Chromatography
Electroanalytic Methods
2
Q
a particle of electromagnetic radiation is known as
A
photon
3
Q
is described as photons of energy traveling in waves
A
Electromagnetic radiation
4
Q
Electromagnetic radiation is spread in the form of
A
electromagnetic waves
5
Q
Electromagnetic radiation energy comes from the
A
SUN
6
Q
The sun gets its energy from the process called______.
A
Nuclear Fusion
7
Q
Distance between identical points on consecutive waves
A
Wavelength
8
Q
Distance between origin and crest (or trough)
A
Amplitude
9
Q
Number of waves that pass a point per unit time
A
Frequency
10
Q
Speed
Formula
A
= wavelength x frequency
11
Q
Wavelength is______ proportional to the frequency of the light wave
A
inversely
12
Q
Energy is_____ proportional to the wavelength of light
A
inversely
13
Q
T or F
The closer the two peaks are, the shorter the wavelength.
The shorter the wavelength, the larger number of photons will be contained in a given distance.
A
TRUE
14
Q
More photons represents more energy, hence,_____ wavelengths represent____ energy
A
shorter
higher
15
Q
: is a wave of alternating electric and magnetic fields
A
Light
16
Q
Light: is a wave of alternating ______ and ______
A
electric and magnetic fields
17
Q
2 types of light
A
Visible
Invisible
18
Q
Invisible light
A
UV
Ifrared
19
Q
- wavelength falls below the visible region (190-340 nm)
A
Ultraviolet
20
Q
Ultraviolet nm
A
(190-340 nm)
21
Q
Infrared, Microwaves, Radio Waves nm
A
More than 700
22
Q
Visible light Wavelength falls within
A
340-700 nm
23
Q
■ also called as “transmitted light”
■ the one that our eyes can see
A
Reflected light
24
Q
White light
■ also called as “________light”
A
polychromatic
25
■ composed of all the visible colors
■ made up of all colors of the rainbow because it contains all wavelengths
■ Ex: Ray of the sun
White light
26
■ Produces only one color
■ Ex: Laser
Monochromatic
27
What is the color absorbed and the color emitted
Wavelength (nm) - 350-400
Violet
Yellow
28
What is the color absorbed and the color emitted
Wavelength (nm) - 400-450
Indigo
Yellow
29
What is the color absorbed and the color emitted
Wavelength (nm) - 450-500
Blue
Orange
30
What is the color absorbed and the color emitted
Wavelength (nm) - 500-550
Green
Red
31
What is the color absorbed and the color emitted
Wavelength (nm) - 550-600
Yellow
Indigo
32
What is the color absorbed and the color emitted
Wavelength (nm) - 600-650
Orange
Blue
33
What is the color absorbed and the color emitted
Wavelength (nm) - 650-700
Red
Green
34
In spectrophotometry, what we’re after is not the light that is_____ by the solution, but the light that is_____ by the solution
reflected
absorbed
35
If the solution is red, the wavelength that is being absorbed is ______
green
36
A hemolyzed (red) solution containing hemoglobin will absorb
green light at 540 nm
37
● States that “ The concentration of a substance directly proportional to the amount of light absorbed and inversely proportional to the logarithm of the light transmitted”.
BEER-LAMBERT'S LAW
38
The relative amount of light passing through the sample is known as_______
Transmittance (T)
39
Percent Transmittance (%T)
T
—- x 100
I
40
○ also called as “Optical Density”
Absorbance (A)
41
is the measurement of the light transmitted by a solution to determine the concentration of the light-absorbing substance in the solution
Spectrophotometry
42
Internal components of Spectrophotometer
1. Light source
2. Entrance slit
3. Monochromator
4. Exit slit
5. Cuvette
6. Photodetector
43
○ “Exciter lamp”
○ Provide the electromagnetic radiation as visible infrared or ultraviolet light
○ Provides energy that the sample will modify by absorption
Light source
44
Types of light sources
■ Tungsten/Tungsten-iodide lamp or Halogen Quartz lamp
■ Mercury Vapor Lamp
■ Deuterium Discharge Lamp
■ Infrared Energy Source
45
most common light source at visible, near UV and near IR
Incandescent tungsten/
Tungsten-iodide lamp or Halogen
Quartz lamp
46
Fluorometry
Mercury*/ hydrogen lamp*/
Xenon arc
47
AAS (Atomic absorption spectrophotometry)
Hollow cathode lamp
48
UV range; continuous light emission down to 165nm
Deuterium
49
Infrared light
Merst Glower
Globar
50
uses an electrically heated rod of rare earth element oxides
Merst glower
51
uses silicon carbide heated to 1200 degrees Celsius
Globar
52
○ Reduce stray light
○ Prevents scattered light from entering the monochromator
Entrance Slit
53
the____ light is allowed to pass through the analytical cell, it would cause a deviation from the readings
stray
54
○ Device that produces light of specific wavelengths from a light source
Monochromator
55
▪ light radiation of a single wavelength
Monochromatic light
56
• defines the range of wavelengths transmitted
• Determines the efficiency of monochromator
BANDPASS
57
Generally, the narrow range of wavelength is the most desirable
Prisms & gratings = <5 nm
Interference filters = 10-20 nm
Bandpass
58
Types of monochromator
1. Prism
2. Diffraction Gratings
3. Interference Filters
59
Wedge-shaped piece of (3) or some other material that allows transmission of light
Prism
glass, quartz, or sodium chloride
60
Prism is based on_____ of light
refraction
61
§ aluminized surfaces that has been cut into tiny grooves that can act as a prism and a slit
Diffraction Grating
62
Diffraction Grating
Based on the principle that_____ bend as they pass a sharp corner.
The degree of bending depends on the______
wavelengths
63
§ based on the principle of constructive interference of waves
§ Only light with desired wavelength which is reflected twice will be in phase and come out of the filter
Interference Filter
64
It is constructed by using two parallel glass plates, which are silvered internally and separated by thin film of dielectric material (CaF2 , SiO, MgF2 ) of different refractive index
Interference Filter
65
○ Exclusion of unwanted light from entering the monochromator
Entrance Slit
66
○ allows only a narrow beam of the spectrum to pass through the cuvette
○ narrows down the light coming from the monochromator
○ Entering to the cuvette
Exit Slit
67
● Analytical cell/sample holder
● Used to hold the solution in the instrument whose concentration is to be measured
● Made of material that does not absorb light in the wavelength range of interest
CUVETTE
68
Types of cuvettes
Borosilicate
Quartz/ plastic
Alumina silica
Soft glass
69
For alkaline solutions cuvette
Borosilicate glass
70
For wavelength below 320 nm cuvette
Quarts or plastic
71
Good at visible regions cuvette
Alumina Silica Glass
72
Preferable for acidic solutions cuvette
Soft Glass
73
● Converts transmitted light energy into an equivalent amount of electrical energy
PHOTODETECTORS
74
Types of Photodetectors
1. Barrier-Layer cell
2. Photoemissive/phototube
3. Photomultiplier
75
○ Photocell or Photovoltaic
○ composed of light-sensitive materials (e.g. selenium on iron plate with transparent layer of silver)
Barrier-Layer cell
76
○ when exposed to light, electrons in the light-sensitive material are excited and are released into the highly conductive silver
○ LEAST EXPENSIVE
○ NO NEED FOR POWER SOURCE
Barrier-Layer cell
77
○ Similar to barrier-layer cell that it has photosensitive material that gives of electrons when light energy strikes it
○ Composed of positively charged anode and negatively charged cathode enclosed in a glass
Photoemissive/ Phototube
78
○ Light strikes cathode → cathode emits electrons → electrons accelerate towards anode
○ Flow of electrons = current = no. of photons
○ Requires an external source of energy
Photoemissive/ Phototube
79
○ Once light strikes the coated electron, electrons are emitted.
○ The electrons are attached to a series of anodes known as_____
Photomultiplier (PM) tube
dynodes
80
The_____ tube can amplify the amount of light energy therefore it can measure even the very low light waves
Photomultiplier
81
○ displays the amount of light transmitted
Read-Out device
82
Read-out devices
1. Meter
2. Digital
3. Recorder
