4.A student places a transparent semicircular block on a sheet of paper and draws around the block. She directs a ray of light at the centre of the flat edge

of the block. Figure 1 shows the path of the ray through the block. 1State why the emergent ray does not change direction as it leaves the block.1 markl 2The student draws an arrow on the paper to mark the incident ray. She marks the path of the emergent ray with crosses A, Band C. She removes the block from the paper and places a protractor over the outline of the block, as shown in Figure 2.