laporan prisma

PRISM
Andi Rezki W AP, Karsimen, Nurpadillah
Laboratory of Basic Physics Department of Physics FMIPA Universitas Negeri Makassar
Abstract
Have been done the practicum about Prism to be able to use the Optic Spectrometer well, understanding the principal of decomposition by prism, and determine the refractive index and dispersi energy of prism. In activity 1, before found the beam of rightside and leftside of prism, we must fined ahead the beam at the center of prism. Then, posted the appointment of scale on the optic spectrometer for the rightside and leftside of prism. For activity 2, samewith activity 1 but the position of prism changed that made certain angle. Because of it, we can found the colour spectrum that consist of seven colour. But we just posting the appointment of scale for red, yellow, and blue. According to experiment result and data analyst, have been obtained the refractive index for red, yellow, and blue are 1.49, 1.511, and 1.515. The wavelength is inversely proportional with its refractive index, therefore can be concluded that red colour had longest wavelength, then yellow and blue. Also have been obtained the energy of dispersi of prism equal to 0.048.
Keywords : Dispersi, spectrum, spectrometer, refractive index, energy of dispersi.

PROBLEM FORMULATION
How to use the Optic Spectrometer well?
How to understanding the principal of decomposition by prism?
How to determine the refractive index and dispersi energy of prism?
PURPOSE
To be able to use the Optic Spectrometer well.
To understanding the principal of decomposition by prism.
To determine the refractive index and dispersi energy of prism.
EXPERIMENTAL METHODOLOGY
Brief Theory
A beam of white light passes through the left side of the prism dropped by a certain angle. The beam will be refracted into the prism and prism will be refracted from the outside to the right side of the prism decomposes into a spectrum of colors: red, yellow and blue. mathematically refractive index (n) prism is
n=sin12 (α + δm)sin 12 α … (6.1)
With α as a prism refracting angle, and the angle of minimum deviation δ_m is. Deviation angle is the angle between the extension of the incident light rays with an extension of bias on the right side of the prism. While the minimum deviation angle smallest angle that can be generated by changing the angle of incidence. The minimum deviation occurs when light through the prism symmetrically
Based on the above equation, then to the spectrum of red, yellow and blue can be derived equation the refractive index of the prism material for a wide range of wavelengths, namely:
nb = sin12 (α + δb)sin 12 α … (6.2)
While the power is power dispersion prism is:
ϕ= nb- nmnk-1 … (6.3)
When a beam of white light entering the surface of a glass prism on some angle, the angle of refraction for shorter wavelengths approaching violet end of the visible light spectrum is slightly larger than the angle of refraction for the wavelength towards the red end of the visible light spectrum. Light with shorter wavelengths larger than the deflected light has a longer wavelength. White light beam spread or be dispersed into component colors. (Tipler, 2010:453)
The color of light associated with the wavelength or frequency of the light. Visible light which is sensitive to light our eyes, fall in the range of 400 nm up to 750 nm. This range is known as the visible spectrum, and there colors from purple to red. Light with a wavelength shorter than 400 nm is called ultraviolet, and cahay with wavelengths greater than 750 nm is called infrared. (Giancoli, 2005: 297)

These experiments using angle measuring instrument called a spectrometer with binoculars. The composition of the spectrometer and its components are shown as the picture below.

SpectrometerTableSlit PlateFocus KnobEye PieceGraticule Lock Ring










Spe
ctrome
ter
Table

Slit Plate

Focus Knob

Eye Piece

Graticule
Lock Ring



Spectrometer components that must be known is:
Collimator
Collimator is a tube fitted with a lens that is dealing with a prism, and a gap that can be set-aturlebarnya facing the light source.
Telescope
This telescope is used to determine the position of the cross thread or color spectrum. Equipped with a lens telescope obyejktif facing directly with the prism, and an eyepiece that can be pulled or pushed. The telescope can also be rotated to the left or to the right. Telescope bottom is equipped with a scale of degrees that can be read on a scale S_1 and S_2 (there are two places to read the scale). Scale which rotates together with the telescope and around the major scale slab called Nonius scale.
Spectrometer Table
This table serves to put the prism. This table can be spun and has a prism refracting angle lock. (Penuntun, 2015:34-35)

The Apparatus
Optic Spectrometer (1 piece)
Equilateral Prism (1 piece)
Magnifier (1 piece)
Spectrum light source of diskrit halogen or mercury (1 piece)
Work procedures
Arrangement early of Optic Spectrometer
Before used, the optic spectrometer must be set-up in such a manner in a normal condition or have been calibrated. Step by step of its setting can be elaborated the following. Ascertaining that the spectrometer on the linear based.
The telescope must be line with collimator and table peddle incision of spectrometer must be line with the optical axis of telecope and the collimator like at picture following.
Tightened the breach-block spanner of telescope and the optic table until do not shift.
Without the grille or prism on the optic table, paid attention the beam by telescope. You shouldly looking the binding vertical line that clear and bold. If not, the wide of gap of collimator is arranged.
Drew near the binding line with the vertical line at telescope.
Arranged it that zero point at especial scale precise near with zero point at scale of nonius under telescope or zero point at scale of nonius with point 180o at especial scale under collimator.
Next, spectrometer ready to use.
Read the spectrometer scale
First determined the value of especial scale: For example, list scale of especial scale is 0.5o.
Then determined amount of nonius scale: Example, amount of nonius scale is 30 scale.
Drew near zero point at especial scale precise near with zero point at scale of nonius. Then determined how much especial scale that near precise with 30 scale of nonius.
For example:
30 scale of nonius = 29 especial scale
So, 30 scale of nonius = 29 x 0.5o
1 scale of nonius = 14.5o/30 = (29/60)o = 29'(29 minutes)
The difference between especial scale with scale of nonius equal:
0.5o – (29/60)o = (30/60)o – (29/60)o
= (1/60)o = 1' (1 minutes)
Activity 1. Determine deflector angle of prism
Arranged the spectrometer like the clarification before.
Prism is placed until one of tip of prism hitting the light from the collimator.
The telescope is turned around to left slowly until seen the light line and drew near with sign "+" at telescope. At this stage, posted how much the read of scale on spectrometer (T1).
Turned back around to right direction slowly until at telescope seen light line. At this stage, posted the appointment scale of spectrometer (T2).
Activity 2. Determine refractive index and energy of dispersi
Arranged the position of prism until one of side of prism made certain angle with collimator
Turned around slowly to left direction until at telescope seen colour spectrum.
After that, while paid the spectrum turned around the prism table in one direction by slowly, so will be seen the shifting spectrum. If the table is turned around to continue (on the same direction), at one time the spectrum will be back to early direction. The position of prism that spectrum precise will be back is position that gave minimun deviation angle. At this stage the prism do not trouble.
Telescope is shifted until sign "+" precise near with the spectrum line of red. At this stage, posted the pisition of telescope (Tr).
Repeated activity (4) for the spectrum of blue (Tb) and spectrum of yellow (Ty).

EXPERIMENT RESULT AND DATA ANALYST
Experiment Result
Activity 1
T0 (reference angle) = 0±0.0167o
T1 = 69.3300±0.0167o
T2 = 58.2000±0.0167o
Refractive angle obtained:
α = T1+T22 = 63.765±0.0167o
Activity 2
Tr = 42.1±0.0167o
Ty = 42.3±0.0167o
Tb = 42.67±0.0167o
Minimum deviation angle obtained:
δr = Tr-T0 = 42.1±0.0167o
δy =Ty-T0 = 42.3±0.0167o
δb =Tb-T0 = 42.67±0.0167o

Data Analyst
Activity 1. Determine deflector angle of prism
α=T1+T22
α=69.3300+58.20002
α=63.765°
Uncertainty
α=T1+T22
α = α T1 T1+ α T2 T2
= 12T1+T2 T1 T1+ 12T1+T2 T2 T2
=12 T1+12 T2
αα =12 T112T1+T2+12 T212T1+T2
= T1T1+T2+ T2T1+T2
α = T1+ T2T1+T2α
=0.0167°+ 0.0167°69.3300+58.200063.765°
=0.0334°127.53°63.765°
=0.017°
RE = αα100%
=0.017°63.765°100%
=0.026%
DC =100-KR%
=100-0.026%
=99.97%
α =α± α°
=63.76±0.01°
Activity 2. Determine refractive index and energy of dispersi of prism
Refrative index
Red
nr =sin12α+δmsin12α
=sin1263.765°+42.1osin1263.765°
=sin52,9325°sin31,8825°
=0.790.53
=1.49
Uncertainty
nr= n α α+ n δr δr
=12cos12α+δrsin12α-sin12α+δr12cos12αsin12α2 α
+12cos12α+δrsin12αsin12α2 δr
nrnr=12cos12α+δrsin12α+δr-sin12α+δr12cos12αsin12α+δrsin12α2 α+12cos12α+δrsin12α+δr δr
nr=12cos12α+δrsin12α+δr-cos12αsin12α α+12cos12α+δrsin12α+δr δrnr
=12cos1263.765°+42.1sin1263.765°+42.1-cos1263.765°sin1263.765°0.017°+12cos1263.765°+42.1sin1263.765°+42.10.0334°1.49
=12cos52.9325°sin52.9325°-cos63.765°sin63.765°0,017°+12cos52.9325°sin52.9325°0.0334°1.49
=120.6020.797-0.4420.8960,017°+120.6020.7970.0334°1.49
=120.75-0.490,017°+120.750.0334°1.49
=0.130,017°+0.3750.0334°1.49
=0.00221+0.01251.49
=0.01471.49
=0.0219
RE = nmnm.100%
=0.02191.49.100%
=1.47%
DC =100-1.47%
=98.53%
nr=nr± nr
=1.49±0.02
Yellow
ny=sin12α+δksin12α
=1.511
ny=12cos12α+δksin12α+δk-cos12αsin12α α+12cos12α+δysin12α+δy δyny
=12cos1263.765°+42.3sin1263.765°+42.3-cos1263.765°sin1263.765°0,017°+12cos1263.765°+42.3sin1263.765°+42.30.0334°1.511
= 120.6010.798-0.8490.5280,017°+ 120.6010.7980.0334°1.511
=0.00803
RE =0.008031.511.100%
=0.53%
DC =100-0.53%
=99.46%
ny =1.511±0.008
Blue
nb=sin12α+δbsin12α
=1.515
nb=12cos12α+δbsin12α+δb-cos12αsin12α α+12cos12α+δbsin12α+δb δbnb
=12cos1263.765°+42.67sin1263.765°+42.67-cos1263.765°sin1263.765°0.017°+12cos1263.765°+42.67sin1263.765°+42.670.0334°1.515
= 120.5980.8-0.8490.5280.017°+ 120.5980.80.0334°1.515
=0.0299
RE =0.02991.515.100%
=1.97%
DC =100-1.97%
=98.021%
nb =1.51±0.02

Energy of Dispersi
Φ=nb-nrny-1
=1.515-1.491.511-1
=0.0250.511
=0.048
Uncertainty
Φ =nb-nrny-1
=nb-nm(nk-1)-1
ΔΦ =δΦδnb nb+δΦδnr nr+δΦδny ny
=ny-1-1 nb+ny-1-1 nr+-nbny-1-1+nrny-1-1 ny
ΔΦΦ = nbnb-nr+ nrnb-nr+-nbny-1-1+nrny-1-2nb-nr(ny-1)-1 ny
= nbnb-nr+ nrnb-nr+-nb+nrny-1-1nb-nr ny
ΔΦ= nbnb-nr+ nrnb-nr+-nb+nrny-1-1nb-ny nyΦ
=0.02991.515-1.49+0.02191.515-1.49+(-1.515+1.49)1.511-1-11.515-1.490.008030.048
=1.196+0.876+-1.9570.008030.048
=0.1150.008030.048
=0.000920.048
=0.0000443
RE = ΦΦ.100%
=0.00004430.048.100%
=0.0002%
Φ = Φ± Φ
= 4.8±0.00410-2

DISCUSSION
According to experiment result and data analyst for activity 1 have been obtained refractive angle of prism α equal to 63.765o. Its mean that angle have been formed between of two surface area of prism is 63.765o
At activity 2 have been obtained the refractive index for red colour = 1.49, yellow = 1.511 and blue = 1.515. According to the theory, we have knew that the longest wavelength is red colour, then orange, yellow, green, blue, and purple. Wavelength is inversely proportional with refractive index, so that red colour have the refractive index that smallest. From the data analyst appointing that refractive index of red is smaller than yellow, and refractive index of red and yellow is samller than blue. Its mean that the longest wavelength is red colour, then yellow and finally blue.
Beside that, at activity 2 have been also dispersi energy of prism equal to 0.048. Energy of dispersi is the ability of prism to elaborating the polychromatic colour (white) to monochromatic colour (red, orange, yellow, green, blue, purple).
CONCLUSION AND DISCUSSION
Dispersi is event of decomposition of light from the polychromatic colour (white) to monochromatic colour (red, orange, yellow, green, blue, purple) that happened passing deflection or deflextion happen
Refractive index of prism is inversely proportional with its wavelength.
Blue light owning biggest refractive index and red light owning smallest refractive index.
SUGGESTION
According to the practicum that have been done there are many mistakes or the trouble that persuing the students work to doing the practicum. The most of mistakes that happened is there are damage of tools when do the practicum, that influencing the data that obtained to done the calculation.
For the official member of laboratory or assistant to increasing the facilities and basic facilities that there, so can be increasing the student performance in our practicum.
BIBLIOGRAPHY
Assistant laboratory of basic physic and Herman. 2015.Penuntun Praktikum Fisika Dasar 2. UNM:Makassar
Tipler, Paul A. 2010. Physic for science and techniquethird edition 2
(Translation).Erlangga:Jakarta
Giancoli. 2005 (terjemahan Yuhliza Hanum). Physic edition 2. Erlangga:Jakarta.