Physics 9702/32 — May/June 2021

Grid A is the grid of parallel, equally spaced lines shown in Fig. 1.1.

Take measurements to determine the average spacing $s_A$ between the centres of the lines on grid A.

$s_A$ = ______ $\text{mm}$

You have been provided with a second grid (labelled grid B) printed on a transparent sheet.

● Place grid B on top of grid A in Fig. 1.1.
● Turn grid B so that there is a small angle $G$ between the grids. A pattern of fringes will be produced, as shown in the example in Fig. 1.2.

● Do not take measurements from Fig. 1.2.

Measure and record your value of $G$ from Fig. 1.1.

$G$ = ______ $^{\circ}$

● The fringes make an angle $F$ with grid A, as shown in Fig. 1.2.

Measure and record your value of $F$ from Fig. 1.1.

$F$ = ______ $^{\circ}$

Rotate grid B and repeat (b) until you have six sets of values of $G$ and $F$.

Use values of $G$ in the range $0^{\circ}$ to $20^{\circ}$.

Record your results in a table. Include values of $\sin F$ and $\sin(F-G)$ in your table.

It is suggested that the quantities $F$ and $G$ are related by the equation

where $p$ and $q$ are constants.

Use your answers in (d)(iii) to determine the values of $p$ and $q$.

$p$ = ______
$q$ = ______

The constant $p$ is related to the spacing of the lines of grids A and B by

where $s_B$ is the line spacing of grid B.

Use your values of $p$ and $s_A$ to calculate $s_B$.

$s_B$ = ______ $\text{mm}$