Glass is a transparent material but glass powder is opaque. Explain.

$ABC$ is a solid glass block. Assuming critical angle for glass as $42°$, complete the path of the ray $PQ$ as it enters the block.

The figure shows three light rays $OA,OB$ and $OC$ from an object $O$ placed in glass $\left(\mu =1.5\right)$ medium. Complete the ray diagram by drawing refracted ray in each case. Locate virtual image of $O$ as $O\text{'}$.

The figure shows a right-angled prism $PQR$. An object $AB$ in front of face $PQ$ of the prism has its inverted image of  same size as $A\text{'}B\text{'}$. Complete the ray diagram to show the image formation. Name the two phenomena used in image formation.

Three light rays $AD, BD$ and $CD$ incident on a glass prism $PQR$. Angles of incidence for these rays are $41°, 44°$ and $48°$ respectively and angles of emergence $42°, 44°$ and $49°$respectively. Which ray suffers minimum deviation? Why?