Answer:
f = q
Explanation:
In the attachment we can see a diagram of the parallel rays.
The dotted line represents the normal to the mirror surface
These rays when reflected using the constructor equation
[tex]\frac{1}{f} = \frac{1}{p} + \frac{1}{q}[/tex]
where p and q are the distance to the object and the image respectively.
Since the rays are parallel P = inf
1 / f = 1 / inf + 1 / q
f = q
this means that all the rays focus on one focal point.
