On Fig. 1.1, draw a normal to the block at point R. Extend your normal 6 cm above side AD and below side BC of the block. Label the point where the normal crosses side BC of the block as T. Measure the angle $\theta$ between SR and the normal. $\theta =$ [BLANK]$^\circ$.
On Fig. 1.1, draw a straight line through the two crosses so that it meets side BC of the block. Mark the point where this line meets side BC with the letter E. Mark the other end of this line as F. Draw a straight line from E to R. This shows the route of the light ray through the block.
Measure the length $a$ of ET on Fig. 1.1. $a =$ [BLANK] cm.
On Fig. 1.1, measure the length $b$ of ER. $b =$ [BLANK] cm.
On Fig. 1.1, extend the line FE into the block until it meets the line RT. Label the point where FE meets RT with the letter G. Measure the length $c$ of line EG on Fig. 1.1. $c =$ [BLANK] cm.
Use your values from (c)(i) and (c)(ii) to work out a first value $n_1$ for the refractive index of the block. Use the equation shown. $n_1 = \frac{b}{2a}$ $n_1 =$ [BLANK].
Use your values from (c)(ii) and (d) to work out a second value $n_2$ for the refractive index of the block. Use the equation shown. $n_2 = \frac{b}{c}$ $n_2 =$ [BLANK].
If two values differ by no more than $10\%$, they may be regarded as the same within experimental accuracy. Compare your value $n_1$ for the refractive index from (e)(i) with the value $n_2$ from (e)(ii). State whether your two values can be regarded as the same. Support your statement with a calculation.
Careless measurement is one source of inaccuracy in this experiment. Suggest a different source of inaccuracy in this experiment.