In an optics experiment, with the position of the object fixed, a student varies the position of a convex lens and for each position, the screen is adjusted to get a clear image of the object. A graph between the object distance $u$ and image distance $v$, from the lens, is plotted using the same scale for the two axes. A straight line passing through the origin and making an angle of $45°$ with the $\mathrm{X}$-axis meets the experimental curve at $\mathrm{P}$. The coordinates of $\mathrm{P}$ will be

Two Plano-concave lenses $(1 \mathrm{and} 2)$ of glass of refractive index $1.5$ have radii of curvature $25 \mathrm{cm}$ and $20 \mathrm{cm}$. They are placed in contact with their curved surfaces towards each other and the space between them is filled with liquid of refractive index $\frac{4}{3}$, Fig. Then the combination is

A point object is placed at a distance of $20 \mathrm{cm}$ from a thin Plano convex lens of focal length $15 \mathrm{cm}$. The plane surface of the lens is now silvered Fig. The image created by the system is at 

Which of the following is true for rays coming from infinity ?