For a concave mirror, if a virtual image is formed, the graph between $m$ and $u$ is of the form:

In a movie hall,the distance between the projector and the screen is increased by $1\%$. The illumination on the screen is:

$A$ particle is oscillating on the $X-$ axis with an amplitude $2\, cm$ about the point $x_0 = 10\, cm$ with a frequency $\omega $. $A$ concave mirror of focal length $5\, cm$ is placed at the origin (see figure). Identify the correct statements.
$(A)$ The image executes periodic motion
$(B)$ The image executes non-periodic motion
$(C)$ The turning points of the image are asymmetric w.r.t the image of the point at $x = 10\, cm$
$(D)$ The distance between the turning points of the oscillation of the image is $\frac{100}{21}\, cm$

$A$ lamp is hanging at a height of $40\, cm$ from the center of a table. If its height is increased by $10\, cm$,the illuminance on the table will decrease by what percentage?

An object is placed on the principal axis of a convex lens of focal length $10\,cm$ as shown. $A$ plane mirror is placed on the other side of the lens at a distance of $20\,cm$. The final image produced by the plane mirror is $5\,cm$ behind the mirror. The distance of the object from the lens is $............cm$.

Three identical convex lenses each of focal length $f$ are placed in a straight line separated by a distance $f$ from each other. An object is located at $f/2$ in front of the leftmost lens. Then,