In the figure shown,if the object $O$ moves towards the plane mirror $M_1$,then the image $I$ (which is formed after successive reflections from $M_1$ and $M_2$ respectively) will move:

An optical arrangement consists of two concave mirrors $M_1$ and $M_2$,and a convex lens $L$ with a common principal axis,as shown in the figure. The focal length of $L$ is $10 \text{ cm}$. The radii of curvature of $M_1$ and $M_2$ are $20 \text{ cm}$ and $24 \text{ cm}$,respectively. The distance between $L$ and $M_2$ is $20 \text{ cm}$. $A$ point object $S$ is placed at the mid-point between $L$ and $M_2$ on the axis. When the distance between $L$ and $M_1$ is $n/7 \text{ cm}$,one of the images coincides with $S$. The value of $n$ is. . . .

$A$ photograph of the moon was taken with a telescope. Later on, it was found that a housefly was sitting on the objective lens of the telescope. In the photograph:

An opaque card is held over the lower half of a converging lens as shown in the figure. Which picture best shows the image that appears on the screen?

Assertion : $A$ red object appears dark in the yellow light.
Reason : The red colour is scattered less.

For a concave mirror,if a real image is formed,the graph between $\frac{1}{u}$ and $\frac{1}{v}$ is of the form: