Question

When you see a straw in a glass of water it looks bent, why is this?

Answer 1

Please see below.

Explanation:

When a ray of light coming from a denser medium enters a rarer medium, it bends outwards (i.e. away from the normal at the surface).

Due to this, they appear to emerge from a point different from the point they actually emerge, see the figure below:

Hence the straw appears bent.