How should I structure my experiment report?

A good template structure for scientific report writing might be as follows: title page, abstract, introduction, theory, description of apparatus, experimental procedure, results, conclusions, references, and appendices.

To break this down a little, I suggest your title page includes clearly your name, the date of submission, report title, and institute name.

Your abstract should outline what the report is about, and detail any conclusions (be they quantitative or qualitative). Try and keep it to one paragraph.

The introduction should lay out the context in which this research was conducted, the motivations for producing the report and hence also its objectives.

Any theory section should, naturally, include the theoretical physics behind the report/experiment. If you were investigating the photoelectric effect, for example, it would be necessary to explain what the 'textbook' physical behaviour is expected to be: this is basically what you'll compare your experimental results with.

Description of apparatus should be brief and clear, and include figures, describing the apparatus used in the experiment.

Experimental procedure should be a little like an instruction manual, though you should still write it in prose: it will explain how to conduct your experiment, eg. what to measure, how, when etc.

Detailing your results is one of the biggest parts of a report: don't just list tables and graphs. You should outline exactly how your many data elements were analysed, how errors were considered/analysed, and include only relevant graphs and tables of overarching results, often quoting a definitive final finding of the report.

Conclusions should introduce nothing new: briefly reiterate what the research aimed to achieve and what you have in fact discovered. You might have verified a model, or completely disproved it! Note also that scientists often read only the abstract and conlusions of a report when conducting initial research before deciding which papers to read in greater depth.

Your references should be a simple numbered list of all the sources you accessed while conducting your research and which contributed to the content of your report: be sure to quote book titles, authors, publishers, dates of publication, page numbers ideally etc. Quote web addresses sparingly, since they disappear over time.

Lastly, any appendicies should be lengthy pieces of supporting work which weren't directly relevant to the main body of the report (perhaps a long-winded error analysis), and as such are included only retroactively.

All of your references and appendicies should be referenced in relevant parts of the main body of the report. eg. 'The supporting derivation of Equation (1.3) describing photon diffraction[2] is included in appendix 1.'