1. Preparation for SPA Notes from PR 8

2. Conducting Experiment • Ensure pins are sufficiently (at least 5 cm) apart. • Why? • Ensure pins are placed vertically • Why? • Read instructions carefully!

3. Recording data • Units in headings of table, not in body • Remember: sin i and sin r has NO units. They are ratios! • Take note of units of calculated values. • Take note of s.f. of calculated values! (stick to 3 s.f.) • Remember no. of d.p. when you record readings!

4. Graphs • Label all major axes gridlines, at 2 cm intervals. • remember the starting points! • Choose a good EVEN scale! • Try to make sure DATA POINTS cover at least 5 squares horizontally and 6 squares vertically (half of graph paper). • If possible, include origin (not so important) • Do not force your graphs through origin! Do a best fit according to your data points.

5. Gradient • Choose good points on best fit line to draw the triangle • Make sure triangle is large • Label coordinates of triangle • Show substitution of coordinates when you calculate gradient! • Remember s.f.!!

6. Precaution/ Source of error • Precaution should be justified • Do … so as to … • For sources of error, do try to describe how it affects your reading. • Which reading would it directly affect? Or which part of the procedure would it affect?