EXPERIMENTAL OPTICSEXPERIMENTAL OPTICS

J.M. Saiz2009

A course in English…A course in English…

• Some disadvantages, but also:

- Getting used to it (future Erasmus, courses and jobs)

- Added value for your credits (enrich your CV)

- Every help with the language whenever required .

- Science lecturers in other countries have not necessarily

English as a mother language.

• Other issues:

- Mixed groups with Erasmus students… if possible.

- Technical vocabulary needs extra practice: so, practise!

• But taught by Spanish lecturers.

- Spanish phonetics, mistakes…but courses are about Physics!

· There will be no ordinary Virtual Course

· Course web-page:Start: www.optica.unican.es

Clic: “Docencia”

Clic: “Experimental Optics”

· MATERIALS:

Guides for the experiments (in English)

The Course programme, callendar, etc.

Examples of past evaluations

Marks, when available

This presentation

…

Sessions organized in Sessions organized in modulesmodules: : DistributionDistribution

THEORY: 2 modules during the first week

T, T

REST: Modules for repetitions, personal work, delayed experiments…

Rep

Rep

CONTROLS (seminars): 1 or 2, depending on the numbers

Cont Cont

Prác

Prác

Prác

EXPERIMENTS: 7 modules each group

Prác

Prác

Prác

Prác

Prác

Prác

• Laboratory Sessions:

• Work in groups: 2 students each group.

Wednesday

(16h – 19h)

All groups

Sessions organized in Sessions organized in modulesmodules: Work: Work

• Individual evaluation.

• Seminars: Probably in the Seminario de óptica (3rd floor)

Week 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Day 25Feb 3M 11M 18M 25M 1Ap 8Ap 22Ap 29Ap 6My 13My 20My 27My 3Ju

Wed

nesd

ay ( 4 to 7 p

m )

P1P2

P3aP3bP4P5P6P7

Th

eory

Th

eory

G1*G2*

-

----

---

G2*G1*

--

-G1*

--

G2*-

G2-

G1

----

--

G1-

G2--

C

--

G2

G1---

---

G2--

G1-

G1**G2**

-----

Op

R

G2**G1**

Op

G1**

R

G2**Op

R

Op

Calendar 2009Calendar 2009

· Labels ‘*’ and ‘**’ correspond to experiments carried out separately by two parts of the same group.

· Op : Optional experiment

· R : Available for changes or repeated experiments

· C : Seminar, session

ExperimentsExperiments

• There will be 6 experiments in 7 sessions, plus another optional.

• The experiment must be prepared beforehand. A careful reading is enough, most of times.

• You are going to be asked about it once in the lab)

Control Sessions : SeminarsControl Sessions : Seminars• Individual (15 min, aprox.). Some hints:

-Briefly Describe the objetive and the work

-Show results and comments.

-Remarks about what is interesting, too difficult, etc.

-Suggestions

-Freedom for other squemes, historic

introductions…

• Students receive questions (5-10 min)

• The student making the presentation is evaluated, and also

others taking part in the discussions (positive evaluations)

• Attendance compulsory for the evaluación continua system

• Experiments chosen by the students should be different from

each other as long as it is possible.

Wednesday 22 de Abril

Control Sessions : DatesControl Sessions : Dates

Where comes the mark from?Where comes the mark from?

• Experiment quality.(A draft summary is handed to the

supervisor AND a laboratory

notebook is kept by each student

• Seminar (15%)

• 1 experiment report (15%)

(chosen by the student), 7

pages)

EV

ALU

AC

ION

CO

NTIN

UA

(7

0%

)

• Exam: (30%)

Nombre ...Grupo ...Fecha ...Preguntas,Realización y Resultados:

• Questions and communication during the experiment

(40%)

Notebook, seminar, report, exam…Notebook, seminar, report, exam…

• The seminar should be understood by somebody who hasn’t

perform the experiment. There is not a mandatory esqueme,

but it should reasonably introduce the subject and explain the

development, main results and a discussion.

• The notebook is a personal account of what is done in the lab.

A separate summary containing only the measurements and the

main results must always be handed to the supervising person.

(Sometimes error calculations may be given later)

Notebook, seminar, report, exam…Notebook, seminar, report, exam…

• The report should follow some standard squeme, for instance

that containing a summary, an introduction, the results and a

discussion. A good suggestion is to include the answers to the

questions proposed in the guidelines of the experiments. This

report should look like the one you would like to present after

finishing the lab work if you had enough time. A maximum of 7

pages is proposed, to avoid lengthy works. The experiment

chosen for the report should be different to that of the seminar.

• The exam contains 4 or 5 questions about the development of

the experiments. Some examples ot these questions can be

found in the web of the course Técnicas Experimentales-4,

which link is next to this.

SupervisorsSupervisors

José Mª Saiz (coordinator)Fernando MorenoPablo Albella

Next…Next…• A description of the experiments

- Not complete!

- Not to substitute the work with the experiments guide

- The lab is the best place to understand the experiments, but…

- …some procedures and ideas are easier in the classroom.

Experiment N.1Experiment N.1

H H´F F´

O O´

a a´

z´z

f´f

Find out the principal planes and the focal planesH, H’F, F’

f , f ’

-Because of the object points chosen to apply the procedure we shall find ALSO the position of the first and last diopters, and the thickness of the lens.

- From our measurements we will assess f ’ y FF’

1.- We must align the system2.- We need to produce a collimated beam3.- We shall measure a complete set of points on the optical bench

H H´F F´ O O´

a a´

z´z

f´f

Fig.1. Correspondence equations connect object and image positions for a system of given focal length. The origin may be taken either in the principal planes (positions a, a´) or in the focci F, F’,(positions z, z´). In this experiment we shall use the latter. z · z’ = - f´ 2

-(1/a) + (1/a´) = (1/f´)

Point- like sourceSource

Collimating Lens

Unknown system

Microscope TT

L

Alignment:

Experiment N.1Experiment N.1

Experiment N.1Experiment N.1

H H´F F´

O1

z1

O1´

z´1

LIGHT

| z´1 |

In order to measure z1 we need to observe the other side…... ¡or better turn the lens!

x1x3

Experiment N.1Experiment N.1

H H´F F´

O1

G

z1

O1´

z´1

H´ HO2 O2´

F´

F

G

O2

z2 z´2

O1

LIGHT

LIGHT

| z1 |

f´

x’1x’2

Experiment N.1Experiment N.1

H H´F F´

O1

G

z1

O1´

z´1

H´ HO2 O2´

F´

F

G

O2

z2 z´2

O1

LIGHT

LIGHT

x4

FF´

f´HH´

Experiment N.2Experiment N.2

2d

2d sen = k

Part 1) For a given (known) We measure and calculate d .

Part 2) For another (unknown) We measure and calculate (using d )

Experiment N.2: Preparing the Experiment N.2: Preparing the GoniometerGoniometer

Angular Scale(1’ resolution nonius)

T1

T2

T3

Collimating arm

Telescope arm

Platform

Source [Na lamp]Slit

1st) Place the reference (cross) with a vertical line. It is placed in the intermediate image.

3rd) Place the focal points of the telescope to infinity shifting the eyepiece with the lateral wheel. We shall use an external collimator for this.

2nd) Place the eyepiece in its frame so that the cross is seen sharply.

TELESCOPE ARM:

Experiment N.2: Preparing the Experiment N.2: Preparing the GoniometerGoniometer

Angular Scale(1’ resolution nonius)

T1

T2

T3

Collimating arm

Platform

Source (Na lamp)Slit

1º) Put the telescope arm in front of the collimator (removing the platform)

3º) Adjust the collimator wheel till we can see a sharp image of the slit

2º) Observe the slit through the telescope arm

COLIMATOR:

4º) Vary the slit width (as narrow as possible but still bright)

+ LEVEL THE PLATFORM:T1, T2 y T3

+ ALIGN OBJECT (IF NECESSARY)Telescope arm

• Angles are measured by taking differences

• Angular scale: There is a sexagesimal Vernier

• Alignment of the grating: same at both sides

2d

Fixed scale

0 10 20 30

Travelling scaleIn 0.5° steps

Accuracy: 1’

Experiment N.2: Preparing the Experiment N.2: Preparing the GoniometerGoniometer

[Symmetry in the observation]

can be either measured or given ( with an error ±1´)

Basis of the method: Refraction law

´

´n

Fig.1: Refraction of a collimated beam (represented by a single ray) in the flat faces of a glass prism. is the main angle of the prism, the diedric angle, and is the total deviation, that shows a minimum, m.

m and the index n are connected:

2

2

sen

senn

m

Experiment N.3. Refraction index Experiment N.3. Refraction index measurement: using a prismmeasurement: using a prism

Prepare the goniometer

3

4

2

1

5

6 7

8

9

10

11

Abbe’s refractometer

Experiment N.3. Using a refractometerExperiment N.3. Using a refractometer

Fig.3: Border line separating the bright and dark regions. The origin is the critical angle when passing from a dense media (bottom prism) to other less dense (liquid of unknown index). The instrument uses an extense source, but the effect is already clear by representing a point source.

Liquid of Unknown index

Source

Eye

Right eyepiece

Intermediate Focal Plane

Collecting Lens

High-index Prisms

Resulting curve is checked with the value obtained before (Yellow)

We measure n for two lines (two ): Red and Green in Na lamp

Simplified Cauchy’s

disperssion formulae

n() = A + B / 2

From the analytical curve, an estimate of

the Abbe number can be made:V =

CF

d

nn

n

1

Experiment N3. Part b: DisperssionExperiment N3. Part b: Disperssion

Fig. 1 Scheme of the measuring system. (Points 1 to 7 are inside the monochromator instrument)

1.- Source2.- Lenses3.- Mirror4.- Entrance slit5.- Reflection diffracton grating. (BASIC DISPERSION COMPONENT OF THE MONOCHROMATOR)6.- Wavelength adjustment wheel7.- Output slit8.- Color filter9.-Photodetector10.- Power source (V-constant) for the detection circuit 11.- Voltimeter12.- Controlling computer.

2

3

42

5

6

7

8

9

11

12

1

10

Experiment N4: Color FiltersExperiment N4: Color Filters

Fig. 2 Detection System. (Items 9 to 12 in the scheme of Fig.1)

(*) Only if connected with a data acquisition system.

Vs

F

+

V

10 K

(*)

T

0

1

Experiment N4: Color FiltersExperiment N4: Color Filters

Figura 1. LEFT: Set-up for the interference fringes experiment with Fresnel’s biprism: upper view. S is the source (slit); S1 and S2 are the positions of the virtual slits (the distance between them is of the order of a fraction of- to a few mm, though in the scheme is made artificially large for the sake of clarity. Darkened area is the superposition region, where fringes can be observed on a screen, for instance , located inside that region. CENTER: Detail of the interference construction in the center of the screen: Wavefronts coming from S1 and S2 are separated /2. Black and hollow dots stand respectively for constructive and destructive superposition, therefore producing an irradiance variation distributed in lines, known as interference fringes (RIGHT)

d

S1

S2

S

D

y

Experiment N5: InterferencesExperiment N5: Interferences

21LLdd may be difficult to measure… directly

21

22

,,

22

,,

22

,,

DDdy

dDdy

yDdy

Ddy

Error:

D

dy

Calculating :

The plane is observed with an eyepiece.

Experiment N5: InterferencesExperiment N5: Interferences

E

E

E cosE sen

E cosE senFig.2 Linearly polarized beam through a “/4” wave plate. The result is a centered elllipse.

Fig. 3 Sequence of elements on the bench for the realization of the experiment

LámpPolarizer Collimating arm of

the goniometerDiaphragm

“/4” AnalizerPhotodetector Meter

Experiment N6: Polarized beamsExperiment N6: Polarized beams

Fig.1 Description of the situation in which no light is observed as reflected from the prism. This is a combined effect of:a) The incident polarization given by polarizer P (that must be parallel to the plane of incidence) – plane of the screen in this drawing.b) The angle of incidence (that must be the Brewster angle ).

SourceP

Prism

n

No reflected light!

Collimator

¿How do we measure the elipticity of an elliptically polarized beam? máx

mínI

Ie

Experimental point: the “zero” of the detector. Coarse and fine adjust

Experiment N6: Polarized beamsExperiment N6: Polarized beams

Fig.1 Image capturing system. Images are formed on a bright screen.

MATERIALS

• CCD camera + Objective lens.

• Control PC + Digitalizer card.

• Post + travelling holder + adapter

• Extended source

• Opaque discs of the same size

• Auxiliary objects, coins, discs, etc

Experiment N7: Digital ImagesExperiment N7: Digital Images

First Objective. Get familiar with some basic operations:

Image Capturing

Study Single Points Of An image

Obtain And Understand Grey Histograms

Make Simple Operations On An Image

Make Operations Between Different Images

Second Objective. Apply the basic operations to some

functions on images:

1) Check the degree of homogeneity of an extended source.

2) Count the objects in the captured image.

3) Dettect movement and measure its magnitude.

Experiment N7: Digital ImagesExperiment N7: Digital Images