All of the following statements are correct except (for a real object):

An object of length $6 \ cm$ is placed at a distance of $4f$ on the principal axis of a concave mirror of focal length $f$. The length of the image will be ......$cm$.

$A$ driver sitting inside a parked car is watching vehicles approaching from behind with the help of a side-view mirror,which is a convex mirror with a radius of curvature $R = 2 \ m$. Another car approaches from behind with a uniform speed of $90 \ km/h$. When the car is at a distance of $24 \ m$ from the mirror,the magnitude of the acceleration of the image in the side-view mirror is $a$. The value of $100a$ is $m/s^2$.

An object is placed in front of a spherical concave mirror between the focal point $(F)$ and the center of curvature $(C)$. Its image is:

Suppose that the lower half of the concave mirror's reflecting surface in the figure is covered with an opaque (non-reflective) material. What effect will this have on the image of an object placed in front of the mirror?

At what distance in front of a concave mirror of focal length $30\; cm$,should an object be placed (in $cm$) so that its real image of size three times that of the object is obtained?