Modern Optics Lab

Modern Optics Lab

Introductory Meeting

Modern Optics Lab

Contact InformationGernot LaicherSouth Physics 410(801) 585-5553gernot@physics.utah.edu

TAs: Joel Brownstein (Wednesday Section)joelbrownstein@astro.utah.edu

Bijaha Thapa (Thursday Section)bijayathapa104@yahoo.com

Bryant Svedin (Tuesday and Friday Sections)bsvedin@gmail.com

Website: http://www.physics.utah.edu/~gernot/Modern Optics/Modern Optics.html

Modern Optics Lab

Lab Format• Lab descriptions will be on our website (pdf files).

• Before the lab: * Read through lab description.* Try to understand the principle of the experiment and the data evaluation methods.* Think about the format of your lab report.

• Labs are done individually, not in groups.

• A short introduction/overview to the lab activity is usually given at the beginning of the lab.

• Lab report is written as much as possible during the lab. Submission deadline is 1 week after lab completion.

• 9 labs (11 lab sessions) are planned over the course of the class (may vary).

Modern Optics Lab

Grading in Modern Optics• Quizzes: 15%• Midterm Exams: 20%• Final Exam: 30%• Lab Grade: 35%

• Your lab score is obtained as follows:90%: Grade received for lab reports10%: General Lab conduct

- Displayed interest/diligence in lab activity- Ability to answer questions asked by TA- Cleanliness of workspace at the end of the lab- Creativity- Punctuality

There is a 10% grade deduction for every day the lab report is late.

Modern Optics Lab

Guidelines for Writing the Lab Report

• Keep in mind the main purpose of a lab report which is a written record of the

a) purpose of the lab activity,

b) methods and techniques - experimentally and mathematically,

c) raw data as measured and their uncertainties,

d) data analysis (e.g., computations) including error propagation,

e) conclusions derived from your data analysis.

• “Say what needs to be said” as efficiently, concise, and clear as possible – we

are not writing novels.

• A picture is worth a thousand words:

Include a sketch of the apparatus when describing the methods.

Label what’s on the sketch.

• Don’t forget units !

• Don’t submit messy lab reports in which the TA needs to “fish for information”.

Modern Optics Lab

Lab Report Grading • General guideline (may vary somewhat depending on lab activity and

TA):

20% Purpose, Methods, Techniques …..

30% Raw Data Record

20% Data Analysis

10% Error calculation

- Measurement uncertainties in raw data

- Propagation of error

20% General appearance and organization

- Legible ?

- Looks organized ?

- Easy to follow ?

Modern Optics Lab

Missing a lab due to Illness, etc.

• Arrange with the TA a way to make up the missed lab activity.- If possible, in another section the same week.- Alternatively a time outside the regular lab hours may be arranged between you and TA.- Worst case: We may waive a lab and base your grade on the remaining average.

You cannot expect to be allowed to make up a lab activity without penalty unless you have a very good reason (illness, etc.).

Modern Optics Lab

Sample Lab Report Pages

Modern Optics Lab

Significant Figures and Uncertainty

• Report uncertainties (error) in measurements to one significant digit

• Make sure the position of the least significant digit of the measured value agrees with that of the uncertainty.

cmx 4.08.5

Modern Optics Lab

Estimating and Reporting Uncertainty

• Estimation of uncertainty from a single measurement due to measuring device (e.g., ability to read out a scale)

• Uncertainty in repeated measurements and averaging (averaging 5 or more measurements to get mean)

calculate standard deviation of the mean

deviation Standard

mean theofdeviation Standard

x

x

N

xx

Modern Optics Lab

Error Propagation

• Calculating the error in the final result based on the error in the measured quantity can be done in several ways.

a) Calculate the “high” and “low” possible outcome based on using extreme values of input data (x+x and x-x).

b) Doing a “proper” error calculation.

Modern Optics Lab

“High/Low” Method

Suppose you measure a quantity and it’s uncertainty

….and you want to calculate the value of a function f(x) and the uncertainty f of the function f(x) at the point x=xo

oo xx

2xxf 3.05.2 ox

Modern Optics Lab

f(x)=x^2

0

5

10

15

0 1 2 3 4x

f(x)

ox

oo xx oo xx

oxf

oo xxf

oo xxf

Modern Optics Lab

f(x)=x^2

0

5

10

15

0 1 2 3 4x

f(x)

ox

ox2

oxf

oo xxf

oo xxf

oxf '

oxf2

2'''2

2oooooo

o

o xxfxxfxfxfx

xf

Modern Optics Lab

........xf

General Error Propagation Method

......),,(222

zz

fy

y

fx

x

fzyxf

..............,, zyxf

2

)(

xdx

dfxf

Modern Optics Lab

Example

6.04.27

4.02.34

03.052.1

sinsin

2

1

1

2211

n

nn

.....8565.1

4.27sin

2.34sin52.1

sin

sin

2

112

n

n

2

22

2

2

11

2

2

11

22

nnn

n

nn

582.34.27cos

4.27sin

2.34sin52.1cos

sin

sin

732.24.27sin

2.34cos52.1

sin

cos

221.14.27sin

2.34sin

sin

sin

222

211

2

2

2

11

1

2

2

1

1

2

nn

nn

n

n

Modern Optics Lab

Example

6.04.27

4.02.34

03.052.1

sinsin

2

1

1

2211

n

nn

.....8565.1

4.27sin

2.34sin52.1

sin

sin

2

112

n

n

06.86.1

056.0

1806.0582.3

1804.0732.203.0221.1

2

222

2

n

n

Modern Optics Lab

Example using “High/Low” Method

6.04.27

4.02.34

03.052.1

sinsin

2

1

1

2211

n

nn

09.02

766.1952.1

2

....766.10.28sin

8.33sin49.1

sin

sin

....952.18.26sin

6.34sin55.1

sin

sin

min,2max,22

22

1111min,2

22

1111max,2

nnn

nnn

nnn

09.86.12 n Method overestimateserror somewhat