$A$ concave mirror is used to form an image of the Sun on a white screen. If the lower half of the mirror were covered with an opaque card,the effect on the image on the screen would be

An object placed in front of a concave mirror of focal length $0.15 \,m$ produces a virtual image,which is twice the size of the object. The position of the object with respect to the mirror is ........... $cm$. (in $.5$)

The focal length of a concave mirror is $50 \ cm$. At what distance (in $cm$) should an object be placed to obtain a real and inverted image of double the size?

In an experiment to determine the focal length $(f)$ of a concave mirror by the $u-v$ method,a student places the object pin $A$ on the principal axis at a distance $x$ from the pole $P$. The student looks at the pin and its inverted image from a distance keeping his/her eye in line with $PA$. When the student shifts his/her eye towards left,the image appears to the right of the object pin. Then,

An object is placed at a distance of $40 \ cm$ in front of a concave mirror of focal length $20 \ cm$. The image produced is

$A$ concave mirror is used to focus the image of a flower on a nearby wall $120 \ cm$ from the flower. If a lateral magnification of $16$ is desired,the distance of the flower from the mirror should be $... \ cm$.