When a parallel beam of white light is incident on a converging lens,the colour which is brought to focus nearest to the lens is

The graph between the lateral magnification $(m)$ produced by a lens and the distance of the image $(v)$ is given by

When a plane wavefront is incident on a convex lens,the emerging wavefront becomes . . . . . . .

$A$ turnip sits before a thin converging lens,outside the focal point of the lens. The lens is filled with a transparent gel so that it is flexible; by squeezing its ends toward its center [as indicated in figure $(a)$],you can change the curvature of its front and rear sides. When you squeeze the lens,the image:

$A$ double convex thin lens made of glass of refractive index $1.6$ has radii of curvature $15 \ cm$ each. The focal length of this lens when immersed in a liquid of refractive index $1.63$ is.......$cm$.

Find the velocity of the image of the given object in $cm/sec$.