A student has obtained a point image of a distant object using the given convex lens. To find the focal length of the lens, he should measure the distance between the:

Select from the following the best experimental setup for tracing the path of a ray of light passing through a rectangular glass slab.

Four students measured focal length of a concave mirror while performing an experiment as shown.

The picture which depicts the correct image formation is:

While tracing the path of a ray of light passing through glass slab as shown in the diagram, four students interpreted the results as given below:

(A) $\angle r>\angle e=\angle i$
(B) $\angle r=\angle e<\angle i$
(C) $\angle i=\angle r>\angle e$
(D) $\angle i=\angle e>\angle r$

The student who has made the correct interpretation is

In the below figure 'S' is the position of the screen on which a sharp image of a distant object (nearly $600 \mathrm{m}$ away from the concave mirror of focal length $10 \mathrm{cm}$) is formed by the mirror 'M'. If the object moves towards the mirror by some distance, say $50 \mathrm{cm}$, then to obtain the sharp image of the object on the same screen again