Presenter: Jerry Plotnick Director, University College Writing Centre

Writing in Physics

A handout on writing in Physics and this slide presentation are available at

http://www.uc.utoronto.ca/physics-handouts

Two types of audience for science writing

• Fellow scientists

• General Audience

Components of a Lab Report

• Title• Abstract• Introduction• Apparatus• Observations• Discussion• Conclusions• References• Appendices

The questions your lab report addresses:

• Title• Abstract• Introduction – Why?• Apparatus – How? • Observations – What did you find?• Discussion• Conclusions• References• Appendices

What does it mean?⎬

Title

• Usually written as a sentence fragment:• e.g. Limits on Anomalous Spin-Spin Couplings

between Neutrons• Can (only very occasionally) be written as a question:• Is CO Carbon KVV Auger Electron Emission Affected

by the Photoelectron?• Determines whether your paper will be read• Should be concise • Should also convey your paper’s most important points

Exercise 1: Can the following title be improved?

Initial observations on the behaviour of various waves in certain media.

Revised: Weakly Turbulent Magnetohydrodynamic Waves in Compressible Low-β Plasmas

Abstract

• Summarizes the entire report in one concise paragraph • Is sometimes not required in lower-year courses• Is usually the last thing that you write even if it appears first

Introduction

1. Gives the purpose of the experiment (can appear last)2. Provides background• introduces the general area of science• reviews key concepts and theory• provides key equations

3. Discusses what is already known

A note on verb tense

When talking about the experiment, write in past tense:

“The objective of the experiment was ...”

When talking about the report, use present tense:

“The purpose of this report is ...”

sample introduction to experiment

In this experiment, the objective is to verify Kirchoff’s Current Law (KCL) and Kirchoff’s Voltage Law (KVL) in a simple electrical circuit. These laws allow us to predict the behaviours of a circuit with a known arrangement of electric components. Ohm’s law states that the voltage (V) across a resistance (R) is directly proportional to the current flowing through it:

Kirchoff’s Current Law (KCL) has two components. The junction law states that the sum of all currents around a junction is zero. The loop law says that sum of all voltage drops around a closed loop is zero [1].

Back- ground

aim

V=RI (1)

Exercise 2: Identify the problem with the following statement of aim from the introduction to an experiment.

In this experiment, the objective is to verify Kirchoff’s Current Law (KCL) and Kirchoff’s Voltage Law (KVL) in a simple electrical circuit.

revised: "The objective of this experiment was to verify Kirchoff’s Current Law (KCL) and Kirchoff’s Voltage Law (KVL) in a simple electrical circuit."

Apparatus (referred to in some disciplines as Materials and Methods)

• Allows your reader to repeat the experiment• Written in paragraph form, not as a bulleted list• Should be concise (less detailed than the lab manual

instructions)• Traditionally written in passive voice, third-person, past

tense (“This was done. That was done”) to emphasize the science, not the scientist, but you can incorporate active voice, first-person, past tense (“I did this. I did that.”)

Exercise 3: Convert the following instructions from a lab manual into part of an Apparatus section.

• Measure the voltage across a 50 Ω resistor• Measure the voltage across a 150 Ω resistor• Record both values

Sentence by sentence conversion:The voltage across a 50 Ω resistor was measured. The voltage across a 50 Ω resistor was measured. Both values were recorded.

Revised further for concision:The voltage across a 50 Ω and a 150 Ω resistor was measured.

In active voice:I measured the voltage across a 50 Ω and a 150 Ω resistor.

Observations

• Provides the substance of your experiment• Presents quantitative results as tables and figures• Always refers to a table or figure somewhere in a

paragraph• Provides captions at the top of a table and the bottom of

a figure• Highlights major findings and trends• Can be in subsections

from Observations section [adapted from: D. Turke et al., App Phys B 92, 159-163 (2008)]: Figure 2 shows the relation between the generated idler power and the input

pump power. The idler power was determined by comparing the spectral integral over the pump with the integration over the idler. With this ratio and the measured pump power the final value could be deduced. The diagram clearly demonstrates a non-linear correlation at low powers. For high pump powers the curve turns into a linear behavior.

Idle

r Out

put P

ower

0

200

400

600

800

Input Power0 20 40 60 80 100

Figure 2. Correlation between the generated idler output power and the input pump power while he signal power is kept constant

Tables versus Figures

Input Power 0 14 18 20 23 28 37 39 44 50 60 69 80 90 100

Idler Output Power 0 72 80 96 102 135 207 233 311 330 431 512 580 624 704

Figure 2. Correlation between the generated idler output power and the input pump power while he signal power is kept constant

Table 2. Correlation between the generated idler output power and the input pump power while he signal power is kept constant

Idle

r Out

put P

ower

0

200

400

600

800

Input Power0 20 40 60 80 100

Discussion

• Shows your analysis and original thinking• Requires the most thought, critical analysis and

interpretations• Addresses the question, “What is the significance of my

results?”• Analyzes in the context of your experiment’s purpose• Makes logical deductions, referring to Observations

section without rehashing it

Questions worth asking in the Discussion section:

• What are the discrepancies between the results I expected and the results I obtained?

• How can I account for the discrepancies?• How might I ensure more accurate results if I were to

perform the experiment another time?• Did I accomplish my experimental objectives?• What are the strengths and limitations of the

experimental design?• How might the design of the experiment be improved?

Conclusion

• No more than one paragraph long• Can address the following questions• What was the significance of my results?• What did the experiment demonstrate about physics?

• In other science disciplines, the conclusion may be absorbed into the Discussion section

References

• Rely on print sources or on electronic sources that are based on published journal articles

• Do not use Wikipedia as a source of information: it is unreliable

• Do not bother to memorize the rules; choose a model and imitate it

numbered-note system (American Journal of Physics)

1

The quantum properties of light are often

associated with wave-particle duality.1,2 By

using modern photodetectors it is possible to

record the arrival of each photon in a beam as

an individual event, if the photon flux is

relatively low. This ability can be used to

demonstrate some quantum effects, such as

single particle interference.3 The quantum

nature of light also has consequences for the

properties of much stronger beams.4 Shot noise

or optical quantum noise is the result of

quantum fluctuations of the intensity of a

laser beam. The formalism of quantum optics has

been spectacularly successful in describing the

quantum state of a laser beam, using the

coherent state or Glauber state.5 There are

three defining features of quantum noise1,4 that

allow a clear distinction between classical

noise and quantum noise.

[Adapted from: J. Morizur, M. Colla, and H. Bachor,

“Quantum noise detection: A portable and educational

system,” Am. J. Phys., 76, 1022–1025 (2008).]

11

References

1 Rodney Loudon, The Quantum Theory of Light,

3rd ed. (Oxford U.P., Oxford, 2004), pp. 117–

123.

2 Claude Cohen-Tannoudji, Bernard Diu, and Frank

Laloe, Quantum Mechanics (Wiley-Interscience,

Malden, MA, 2006).

3 C. H. Holbrow, E. Galvez, and M. E. Parks,

“Photon quantum mechanics and beam splitters,”

Am. J. Phys. 70, 260–265 (2002).

4 Hans-A. Bachor and Timothy Ralph, A Guide to

Experiments in Quantum Optics, 2nd ed. (Wiley,

Malden, MA, 2003).

5 R. J. Glauber, “Coherent and incoherent states

of radiation field,” Phys. Rev. 131, 2766–2788

(1963).

Appendices

• Include raw data, detailed calculations, graphs and other quantitative material that will otherwise crowd the body of your report

• Are always labeled and referred to somewhere in the report

Abstract (revisited)

• Typical size: 100-200 words (1/3 to 2/3 double-spaced pages)

• Contains the report in miniature• Emphasizes results• Belongs at beginning of paper• Avoids specialized language

exercise 4: Identify the component of the lab report that each sentence from the abstract below helps summarize: (a) Introduction, (b) Apparatus, (c) Observations, (d) Discussion, and (e) Conclusions.

In this experiment, a disk pendulum was used to investigate the world of chaos and some of its properties [ ]. A simple setup and a PC computer were used to record the phase space diagrams of the motion [  ]. The constraints in the non-linear equation of motion were determined using a variety of methods [   ]. The moment of inertia of the pendulum was found using the geometry of the system to be 1.433±0.004 e-4 kg m2. The natural frequency of the pendulum was determined using the geometry of the mass to be 3.54±0.02 rad/s, and using the maximum amplitude to be 4.13±0.007 rad/s [  ]. These two values do not agree within experimental error [   ]. The experiment demonstrates that we cannot predict exactly when period doubling will occur if all we are given is the initial conditions, but we can predict the behaviour of the system if period doubling occurs [   ].

a

bb

 cd

e

What is Jargon?

Jargon n 1 a: confused unintelligible language b : a strange, outlandish, or barbarous language or dialect c : a hybrid language or dialect simplified in vocabulary and grammar and used for communication between peoples of different speech 2: the technical terminology or characteristic idiom of a special activity or group 3 : obscure and often pretentious language marked by circumlocutions and long words

(From Webster’s Ninth New Collegiate Dictionary)

What is Jargon?

Jargon n 1 a: confused unintelligible language b : a strange, outlandish, or barbarous language or dialect c : a hybrid language or dialect simplified in vocabulary and grammar and used for communication between peoples of different speech 2: the technical terminology or characteristic idiom of a special activity or group 3 : obscure and often pretentious language marked by circumlocutions and long words

(From Webster’s Ninth New Collegiate Dictionary)

Bad use of jargon in the

humanities and sciences

Good use of jargon in the

sciences

Geology paper with jargon:

The Cretaceous period was a time of great change for land plants. It is thought to have seen the origin of the angiosperms, which exploded in diversity and prominence through the period. It was also a period which saw large numbers of extinctions. These are extremely well documented in the fossil record of marine organisms, and less so for land plants. At or near the end of the Cretaceous period, groups such as Dinosaurs, Belemnites, Rudist bivalves, Ammonites, and many others went extinct (Archibald and Clemens, 1982).

cretaceous: pertaining to a period of the Mesozoic period occurring from 70,000,000 to 135,000,000 years ago and characterized by the extinction of giant reptiles and the advent of modern insects.

Angiosperm: a plant having its seeds enclosed in an ovary; a flowering plant.

Belemnite: a conical fossil several inches long, consisting of the internal calcareous rod of an extinct animal allied to the cuttlefish.

Rudist: a fossil pelecypod bivalve mollusc belonging to the superfamily Rudistacea; which included cone-shaped reef-forming animals.

bivalve: a mollusk having two shells hinged together, as the oyster, clam, or mussel

Ammonite: one of the coiled, chambered fossil shells of a cephalopod mollusc of the extinct order Ammanoidea.

Exercise 5: Improve the following sentences.

a. Members of the medical establishment are not presently cognizant of efficacious treatments resulting in the complete elimination of symptomatology in acute viral nasopharyngitis, which in common nomenclature is referred to as the common cold.

revised: There is no known cure for the common cold.

Passive vs. Active Voice

• I completed the problem set. (active voice)

• The problem set was completed by me. (passive voice)

• The problem set was completed. (passive voice, no actor)

Passive vs. Active Voice

• He talks the talk. But can he walk the walk? (active voice)

• The talk is talked by him. But can the walk be walked by him? (passive voice)

• The talk is talked. But can the walk be walked? (passive voice, no actor)

Mixing Passive and Active Voice

from: Earth's other moon: An exercise in computational dynamics. American Journal of Physics, 2008;76:720–722.

To develop the model we worked through a series of increasingly sophisticated scenarios. We first obtained a solution for two bodies interacting via the gravitation force with the position of the larger body fixed. A MATHCAD program was written to integrate Newton's second law using the Runge-Kutta fourth-order algorithm, and the results were compared with the analytic solution. Then we allowed the larger body to move, thereby examining the relative motion of two mutually interacting bodies.

Exercise 5: Improve the following sentences.

b. The answer was provided to within eight decimal places by the Fourier transform.

revised: The Fourier transform provided the answer to within eight decimal places.

Exercise 5: Improve the following sentences.

d. A scientist must refrain from expressing their emotional reaction.

Revised: A scientist must refrain from expressing his or her emotional reaction. (correct)

Revised: Scientists must refrain from expressing their emotional reactions. (better)

Using tenses in the Sciences

• use present tense for an assertion about nature:The speed of light is constant in all frames of reference.

• use present perfect tense for an action that has occurred in the past but continued up to the present:Over the past several decades physicists have proposed a wide variety of unified field theories.

• use past tense for what you or someone else did or asserted:I observed the refraction of white light through a prism.Einstein published a paper on Brownian motion.

• mix tenses within the same sentence as necessary:Galileo argued that objects fall with uniform acceleration in a vacuum.

Using tenses in the humanities

• use present tense (rather than past tense) for what a writer, an artist, or a scholar wrote or asserted:

Shakespeare compares the poet’s lover to a summer’s day

• use past tense for making an historical assertion about a writer, an artist, or a scholar:

Shakespeare wrote many of his tragedies during a period of great political instability.

Closing Tips:

• always know your audience: are you writing for other scientists or a general reader?

• lab reports follow a set format: understand what each of the sections means, but read your manual carefully for course-specific instructions

• use paragraph form in your lab reports• convey your understanding of the experiment in the

Discussion section• prefer active verb forms where possible, but check with

your TA in other courses whether passive is required in the Apparatus or the Materials and Methods section

• use jargon only when it helps you to convey a complicated concept more concisely

• be clear, concise, and direct: don’t be overly sophisticated