Atomic Spectrometer Laboratory Experiment Analysis

Vicky J. Mawuntu

NIM 10 310 868

Universitas Negeri Manado 2012

ATOMIC SPECTROMETER

A. GOALS OF EXPERIMENT

1. Calibrating spectrometer with Mercury and Neon spectrum by using graph method.

2. Determine the wavelength of the emission spectra of various atoms held various gases

in the tube lamps (Neon and Mercury) and determine the electron transitions.

B. EQUIPMENT AND MATERIALS

1. Spectrometer

2. Neon gas tubes and mercury.

3. Clamp Holder

4. Coil Rumkorf

5. Power suply

6. Prism

C. BASIC THEORY

Light is a transverse wave that includes electromagnetic waves. The properties

include light can experience reflection (reflection), refraction (refraction), stretching

(diffraction), absorbed the vibration direction (polarization), and described (dispersion).

The dispersion of white light into the events unraveling the colorful light. A white

light consists of several color spectrum wavelength divided by each. When a beam of light

passing through a transparent medium it will undergo refraction due to differences in

refractive index medium in its path. White light can be broken down into a colorful light

called polychromatic light while a single light that can not be described again called

monochromatic light.

Dispersion event also occurs when a beam of white light is passed at a prism to form a

spectrum of light. This spectrum can be observed through a spectrometer.

Prism is a transparent substance bounded by two plane. When a beam of light came

on one of the fields which is then referred to as a prism refracting the field I will be refracted

near normal line. Until the field of refractory II, the beam will be refracted away from the

normal line. In the field of refractory I, refracted rays approaching the normal, because the

light coming from the optical substance less dense to more dense optical substances, from air

to glass. In contrast to the field of refractory II, refracted rays menjahui normal line, because

the light coming from the optical substances meeting the optic substance that is less dense

than glass into the air. So that a beam of light passing through a prism will experience

deflection from the original direction.

The image above illustrates a beam of light passing through a prism. The figure shows

that the light beam in a prism having two kalipembiasan so that the light rays enter the prism

and the beam out of the prism is no longer parallel.

The angle formed between the direction of the beam comes to the direction of the

light leaving the prism is called the angle of deviation given the symbol D. The magnitude of

the deviation angle depends on the angle the light comes.

D = i1 + r2 - β

Where:

D = the angle of deviation

i1 = angle of incidence on the prism

r2 = left angle prism light refraction

β = angle peak or angle prism refracting

The amount of light depending on the angle of deviation angle of light coming into

the prism. If the point of arrival of the light is reduced, then the angle of deviation would be

even smaller. Will achieve the minimum deviation angle (Dm) if the angle of incidence of

light to the same prism light refraction angle prism or leave at that beam of light entering the

prism prism will cut it into an isosceles triangle, so it applies i1 = r2 = i (with i = angle), and i2

= r1 = r (with r = angle bias). Minimum deviation angle can be expressed as:

The incident light dispersion can be observed through a spectrophotometer. Beam of

light is used in the form of gas lamps fed high voltage, so that the lamp will emit light rays

with a wavelength-specific (depending on the type of gas used).

By putting the gas lamp (Hg) in front of the collimator, the beam towards one side of

the prism will form on the other side of the spectrum. This spectrum can be observed through

binoculars and note its position by reading the scale. if the spectrum is known wavelength,

the spectrometer can be calibrated, so that the spectrometer can be used to determine the

wavelength spectrum of an unknown substance.

Prism

Prism spectroscope is a device used to view the spectrum of a light source. Prism

spectrometer is an instrument used to measure the spectrum of light that break down after

passing through a medium or to measure the wavelength and the refractive index of a prism.

The composition comprises a prism spectrometer components collimator, telescope,

spectrometer table, and scale.

a. Collimator

Colimator is a tube fitted with a lens akromatik where one end (facing the prism) and

a gap. Collimator lens function is to align the beam coming out of the gap. Gap width can be

set using the regulator screw located on the end near the collimator slit. PC regulator screw is

used to adjust the width of the beam of light falling on the prism of the gap, while the

position of the lens can be set with couplers, PL. In use the prism spectrometer, the gap

associated with the light source to be observed spectra. The light source is enclosed in a tube

(so the light is not scattered) and slit parallel to the gap found on the collimator.

b. Telescope

The telescope is used terdri of objective and eyepiece lenses. The position of the

ocular lens of the objective lens can be adjusted with the screw, which is located on the end

of a telescope. The telescope can be moved-motion, in addition to functioning as a place to

see the spectrum of the light produced prism, telescope is able to show the resulting angle of

refraction prism. To determine the exact position of a gap, is used as a reference cross thread.

c. Table Spectrometer

Spectrometer table is a place for meletkkan prism. His position can be raised /

lowered or rotated by loosening the screws and mengeratkannya. Prism is an object that

distorts the spectrum of the light source.

d. Main Scale and Scale Nonius

Under the spectrometer table, there is a dish of the major scale and Nonius scale.

These scales indicate the resulting corner of refraction lens. In the major scale there are 360

large-scale shows the corner on a full circle. While the Nonius scale scales are smaller. The

number of scales on a scale swordfish Nonius fixed, it depends on the precision spectrometer,

the more Nonius scale and the smaller the distance from the scale of the one and the other,

the accuracy of the spectrometer is small anyway. And errors in the measurement are also

very small.

Working Principle Spectrometer

A spectrometer using a diffraction grating or a prism to separate the different

wavelengths of light. The working principle of the spectrometer is bring light through a

narrow gap called a collimator. This is the focus collimator lens, so that the light will be

transmitted in parallel. Light is parallel, then forwarded to the grid for later captured by

teleskope whose position can be moved. Wavelength measurements can be performed using a

diffraction grating spectrometers placed on the table. When light passes through a grating,

diffraction event occurs. In particular teleskope position is at an angle θ, is the position that

correspond to the pattern of light (maximum pattern).

For the prism spectrometer, parallel light then entered a prism. Here, light dispersion

or events experienced decomposition polikromarik light (white) to light-monochromatic light

because the refractive index difference.

A lens focuses light on out gap. Only one color of light that can pass through this gap

at a time. Therefore, the prism must be rotated to bring other colors into the exit slit and read

the entire spectrum. The scale of the circular noted that angle prism wavelength of light can

be determined.

But there is also a spectrometer that uses flat mirrors called gratting groove instead of

a prism. The surface of a gratting contains thousands of thin parallel grooves. The light that

penetrates gratting will produce a spectrum.

Spectrum Lines

Atomic electron stationary in particular has complete power expressed by numbers -

quantum numbers, namely:

n = 1,2,3, ......... (Called the principal quantum number)

l = 0,1,2, ...... (n-1) (referred to as the orbital quantum number)

ml = - l, (-l + 1), ..... l-1, l (called the orbital magnetic quantum numbers)

ms = ± s

Power of electrons in atoms form a kind of cedar - cedar effort, referred to as cedar

atomic energy, which for the atom - atom with a single electron. According to quantum

theory Bohr expressed as:

(

)

with:

R = 1, 097 x 107 m-1

is called the Rydberg constant

h = 6.625 x 10-34

Js called the Planck constant

c = 3 x 108 m/s as the speed of light.

Z as the atomic number

The electrons in an atom can move from cedar power (energy level) to another power

cedars following selection rules are:

Δl = ± 1 and Δml = 0, ± 1

Displacement of electrons in the atoms of a cedar energy onto a higher power can occur by

absorbing energy from the outside (either heat, kinetic energy, radiation workers, etc.). While

the transfer of electrons onto a lower generally accompanied by the emission of radiation

energy. Radiation of electromagnetic waves emitted by electrons moving from the cedar

force (which has principal quantum number n) to the level power with quantum numbers m

<n has a wave number that can be expressed by the equation:

(

)

where:

λ = wavelength of radiation

With the existence of electromagnetic waves emitted by the transition of electrons -

electrons in atoms emerged as the emission spectra / emission in atoms, which can be any

member information regarding quantitation and cedar - cedar energy of electrons in atoms.

The incident light dispersion can be observed through a spectrophotometer. Beam of light is

used in the form of gas lamps fed high voltage, so that the lamp will emit light rays with a

wavelength-specific (depending on the type of gas used).

In terms of the atomic emission spectrum lies in the visible region facilitate

observation and measurement wavelength. Wavelength as the wavelength spectrum of atoms

can be measured using Higler spectrometer, which was equipped with a wavelength scale.

Alternatively, you can use the new spectrometer equipped with an angular scale of the order

of minutes.

By using Mercury spectrum, where wavelengths are known from the literature:

No. Color λ(Ǻ)

1. Red 6907

2. Yellow 1 5789,7

4. Yellow 2 5769

5. Green 1 5460,6

6. Green 2 4916

7. Blue 4358,4

8. Violet 4358,4

9. Violet 4046,6

for the atom - atom Rydberg constant of the complex has been put on the principal quantum

number correlations in the Bohr formula so that the formula (3) becomes:

(

)

Where a and b is the deviation of the integers n and m, called the quantum defect.

D. STEPS OF EXPERIMENT

1. Set the spectrometer so that the eyepiece apparent cross gari with binoculars on a

collimator way also towards mercury lamp or lamps Helium (in a straight position)

2. Set the lens so that the object observed okulernya apparent.

3. Adjust so that the light from the source collimator looked sharp by adjusting the width

of the collimator slit as narrow as possible.

4. Putting prism spectrometer with a position on the table beside the clear prism-center

directional ketengah objective lens on the collimator.

5. Then pull aside the lenses of binoculars while observing the spectrum.

6. While observing through the lens prism binoculars rotary table so that the observed

spectrum prism moving in the direction of rotation and rotate again to turn the

spectrum reverse direction. Find the position of the turning point of the spectrum

rounds. (As the minimum angle of deviation angle spectrum).

7. By putting the crosshairs in the eyepiece at the position of each spectral line color

then measured how the angle formed by the line color of the spectrum.

8. Replace mercury lamp with Helium gas lights then follow steps 4-7 for each

measurement of the angle of deviation.

E. OBSERVATION DATA

Mercury Lamp

Straightening Angle : Left Nonius = 57

Right Nonius = 237

No Color

I II III I II III

1 Violet 1 16,5 4’ 16,5 4’ 16,5 4’ 196,5 4’ 196,5 4’ 196,5 4’

2 Violet 2 16,5 10’ 16,5 9’ 16,5 10’ 196,5 11’ 196,5 11’ 196,5 11’

3 Blue 16,5 27’ 16,5 27’ 16,5 28’ 196,5 27’ 196,5 27’ 196,5 27’

4 Green 1 17,5 17,5 17,5 197,5 197,5 197,5

5 Green 2 17,5 20’ 17,5 19’ 17,5 20’ 197,5 20’ 197,5 20’ 197,5 19’

6 Yellow 1 18 18 18 197,5 28’ 197,5 29’ 197,5 29’

7 Yellow 2 18 3’ 18 3’ 18 3’ 198 5’ 198 5’ 198 5’

Neon Lamp

Straightening Angle : Left Nonius = 57

Right Nonius = 237

No Color

I II III I II III

1 Violet 16,5 27’ 16,5 27’ 16,5 27’ 196,5 27’ 196,5 27’ 196,5 27’

2 Green 17,5 15’ 17,5 16’ 17,5 15’ 197,5 15’ 197,5 15’ 197,5 15’

3 Yellow 1 18 18 18 198 198 198

4 Yellow 2 18 1’ 18 2’ 18 1’ 198 2’ 198 1’ 198 2’

F. CALCULATION OF DATA

Mercury Lamp

Straightening Angle : Left Nonius = 57

Right Nonius = 237

No Color

I II III Average I II III Average

1 Violet 1 16,57 16,57 16,57 16,57 196,57 196,57 196,57 196,57

2 Violet 2 16,67 16,65 16,67 16,66333 196,68 196,68 196,68 196,68

3 Blue 16,95 16,95 16,97 16,95667 196,95 196,95 196,95 196,95

4 Green 1 17,5 17,5 17,5 17,5 197,5 197,5 197,5 197,5

5 Green 2 17,83 17,82 17,83 17,82667 197,83 197,83 197,82 197,8267

6 Yellow 1 18 18 18 18 197,97 197,98 197,98 197,9767

7 Yellow 2 18,05 18,05 18,05 18,05 198,08 198,08 198,08 198,08

Minimum Deviation Angle on prism of Mercury Lamp

o Violet I

o Violet II

o Blue

o Green I

o Green II

o Yellow I

o Yellow II

Neon Lamp

Straightening Angle : Left Nonius = 57

Right Nonius = 237

No Color

I II III Rata-

Rata

I II III Rata-

Rata

1 Violet 16,95 16,95 16,95 16,95 196,95 196,95 196,95 196,95

2 Green 17,75 17,77 17,75 17,75667 197,75 197,75 197,75 197,75

3 Yellow 1 18 18 18 18 198 198 198 198

4 Yellow 2 18,02 18,03 18,02 18,02333 198,03 198,02 198,03 198,0267

Minimum Deviation Angle on prism of Neon Lamp

o Violet

o Green

o Yellow 1

o Yellow 2

ANALYSIS

The emitted light vary in each gas and is characteristic of the gas. Light produced

helium gas and mercury gas in the lamp, having bending light waves passing through the

lattice, where the smaller lattice, the greater the spread of the wave. Then, the results of the

diffraction of light wave interference, so the binoculars visible color spectrum measured

angle shape.

Based on the calculations for each gas, violet spectrum has the shortest wavelength

and red the longest, ie

Gas Color Deviation Angle (o)

Mercury

Violet 1 40,43

Violet 2 40,33667

Blue 40,04333

Green 1 39,5

Green 2 39,17333

Yellow 1 39

Yellow 2 38,95

Neon Violet 40,05

Green 39,25

Yellow 1 39

Yellow 2 38,9733

Once the minimum deviation angle values obtained will then be sought wavelength of

the fluorescent light source with a wavelength spectrum of colors using a mercury lamp as a

reference. Of libraries used, obtained wavelength spectrum of colors on Mercury lamps are:

Yellow I = 5789,7

Yellow II = 5769

Green = 5460,6

Violet = 4046,6

In this experiment we used a prism to describe the color, with the aim of calculating

the wavelength of each spectrum.

The spectrum of light in the prism of the deflection of light caused by the prism. Prism

consists of two flat fields, diffusers I and II refractory. In the field of refractory I, refracted

rays approaching the normal, because the light coming from the optical substance less dense

to more dense optical substances, from air to glass. In contrast to the field of refractory II,

refracted rays menjahui normal line, because the light coming from the optical substances

meeting the optic substance that is less dense than glass into the air. So that a beam of light

passing through a prism will experience deflection from the original direction and formed a

spectrum of colors.

Dispersion of light is the decomposition of polychromatic light (white light) into a

monochromatic light (red, orange, yellow, green, blue, indigo, violet) by refraction or

bending. Different wavelengths of each color spectrum caused by differences in the angle of

deviation of the color spectrum.

Collimator serves to change the light / light into a parallel beam. Rays coming from

the source is diffuse rays (emanating all directions). By collimator diffuse light is converted

into a parallel beam before it is passed to the prism.

Determining Steps wavelength spectrum of colors by using charts

1. Determine the scale on the graph

2. Determining minimum deviation scale and wavelength (used graphs of minimum

deviation wavelength)

3. Plot points deviation angle which is the result of the experiments conducted

4. Mercury plotting wavelength of each color according to the reference spectrum of

wavelengths that exist in the library Mercury.

5. Determine the point of intersection obtained between the wavelength and the angle

of deviation of each spectrum. Then drag the lines connecting each cut point gained.

6. To determine the wavelength of Neon, note the location of the vertex deviation for

each spectrum and the location of the crossing point on the line spectrum of mercury.

Drag the vertical y-axis direction, until it touches the x-axis. Value read on the x-axis

that is a wavelength for the color spectrum.

40,43

40,33667

40,04333

39,5

39,17333

39 38,95

38,8

39

39,2

39,4

39,6

39,8

40

40,2

40,4

40,6

0 1000 2000 3000 4000 5000 6000 7000

Deviation Angle

Wavelength

MERCURY GAS

Wavelength in accordance with the observations by using graphical method is as follows:

No. Color λ(Ǻ)

1. Yellow 1 5980

2. Yellow 2 5768

3. Green 5332

4. Violet 4348

38,9733 39

39,25

40,05

38,8

39

39,2

39,4

39,6

39,8

40

40,2

0 1000 2000 3000 4000 5000 6000 7000

Deviation Angle

Wavelength

NEON GAS

Comparison of the wavelength spectrum of colors on the gas and the gas Mercury Neon:

No. Color

λ (Ǻ)

Mercury Neon

1. Violet 4046,6 -

2. Violet 4078 4348

3. Blue 4358,4 -

4. Green 1 4916 -

5. Green 2 5460,6 5332

6. Yellow 1 5769 5768

7. Yellow 2 5789,7 5980

Precentage of uncertainty of Color Spectrum on Mercury (Hg) Lamp

From the whole calculation of error precentage, we gain small error for the experiment.

The difference between the results of this lab with the existing theory, due to several possible

factors as follows.

1. The existence of a cracked prism, so that the light coming out of the prism

experienced assimilation, and difficult to see the color difference spectrum

2. Scale reading on the arc angle spectrometer is improper

CONCLUSION

In this experiment is defined wavelength spectrum of colors from neon to calibrate the

spectrometer using a graphical method, based on the wavelength spectrum of atomic

mercury

From the observations made, for Mercury gas spectrum obtained 7 colors, namely

purple I, II purple, blue, green I, II green, yellow I and II yellow. Largest minimum

angle of deviation found in the spectrum of the color purple I and smallest in the

yellow spectrum II. As for the wavelength, the spectrum has the largest wavelength

yellow II, while the smallest in the purple spectrum I.

From the observations made, for Neon gas spectrum obtained four colors, namely

purple, green, yellow I and II yellow. Minimum deviation angle on the spectrum are

the largest and smallest purple on yellow spectrum II. As for the wavelength, the

spectrum has the largest wavelength yellow II, while the smallest in the purple

spectrum.

Wavelength for each of the color spectrum on both the type of lamp, obtained

different results. However, the results did not differ significantly. When compared

with the reference of the wavelength, the deviation error for the determination of the

wavelength for each of the observed spectrum of colors can be quite small. This is

because the possibility of an error (error) in this experiment. Some things that cause

such error is parallax errors when determining crosshead for each line of the observed

spectrum, the less accuracy in the reading of the scale, as well as problems on the

device used.

SUGGESTION

Observers should consider prism is used, you should use a prism that has a good

condition, in order to get the results of the minimum deviation angle light throughput.

In this experiment required accuracy in measuring the angle of each order of the

spectrum. The difficulty of measuring and observing the room quite dark very

influential on the spectrometer scale reading accuracy.

Collimator gap should be set as narrow as possible (note that the observer can still see

the light at the slit collimator) to facilitate placement of crosshead on spectral lines.

Putting crosshead precisely the spectral lines is necessary in order to obtain a

thorough measurement angle.

LITERATURE

J,B. Moningka. 2012. Penuntun Praktikum Laboratorium Fisika I. Jurusan Fisika: FMIPA

UNIMA

http://anitanurdianingrum.blogspot.com/2011/08/laporan-spektrometer-sederhana.html