In this experiment, you will investigate the patterns produced by overlaid grids.

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

1. [1] Final value of s_A to at least two significant figures and in the range 1.05-1.10mm.
2. [1] Evidence that s_A has been correctly calculated from a measurement of at least 10s_A.
3. [1] Value of G in range 0°-45°.
4. [3] Six (or more) sets of readings of G and F (different values) with correct trend (F increases as G increases) and without help from the Supervisor scores 3 marks, five sets scores 2 marks, four or fewer sets scores 1 mark.
5. [1] Range: G_min ≤ 3° and G_max ≥ 17°.
6. [1] Column headings: Each column heading must contain a quantity and a unit where appropriate. Headings for sin F and sin (F-G) must have no unit. The presentation of quantity and unit must conform to accepted scientific convention e.g. F/°.
7. [1] Consistency: All values of raw G and raw F must be given to the nearest degree.
8. [1] Significant figures: Values of sin F should be to the same number of significant figures as, or one greater than, the number of significant figures in the corresponding value(s) of raw F.
9. [1] Calculation: Values of sin (F-G) calculated correctly.
10. [1] Axes: Sensible scales must be used, no awkward scales (e.g. 3:10 or fractions). Scales are chosen so that the plotted points occupy at least half the graph grid in both x and y directions. Axes must be labelled with the quantity that is being plotted. Scale markings should be no more than three large squares apart.
11. [1] Plotting of points: All observations in the table must be plotted on the grid. Diameter of plotted points are < half a small square. Points must be plotted to an accuracy of half a small square.
12. [1] Quality: All points in the table must be plotted (at least 5) on the grid. Trend of points on graph must be correct. It must be possible to draw a straight line that is within ± 0.02 on the sin F axis of all plotted points.
13. [1] Line of best fit: Judge by balance of all points on the grid about the candidate's line (at least 5 points). There must be an even distribution of points either side of the line along the full length. Allow one anomalous point only if clearly indicated by the candidate. There must be at least five points left after the anomalous point is disregarded. Lines must not be kinked or thicker than half a small square.
14. [1] Gradient: The hypotenuse of the triangle used must be greater than half the length of the drawn line. Method of calculation must be correct, i.e. Δy /Δx. Gradient sign on answer line matches graph drawn. Both read-offs must be accurate to half a small square in both the x and y directions.
15. [1] y-intercept: Correct read-off from a point on the line and substituted into y = mx + c. Read-off must be accurate to half a small square in both x and y directions. or Intercept read directly from the graph at x = 0, accurate to half a small square.
16. [1] Value of p equal to candidate's gradient and value of q equal to candidate's intercept. Values must not be written as fractions.
17. [1] Values for p and q both given without a unit.
18. [1] Correct calculation of s_B using s_B = ps_A.