$A$ convex lens is made up of three different materials as shown in the figure. For a point object placed on its axis,the number of images formed are

$A$ diminished image of an object is to be obtained on a large screen $1\, m$ from it. This can be achieved by

The sun subtends an angle of $(1/2)^o$ at the surface of the earth. $A$ converging lens of focal length $100\, cm$ is used to obtain an image of the sun on a screen. The diameter of the image formed is about.....$mm$.

Two convex lenses of focal lengths $f_1$ and $f_2$ form images with magnification $m_1$ and $m_2$, when used individually for an object kept at the same distance from the lenses. Then, $f_1 / f_2$ is

$A$ convex lens forms a real image of an object for its two different positions on a screen. If the height of the image in both cases is $8 \ cm$ and $2 \ cm$,then the height of the object is ........ $cm$.

$A$ convex lens of refractive index $1.5$ and focal length $f = 18 \ cm$ is immersed in water. The difference in focal lengths of the given lens when it is in water and in air is $\alpha \times f$. The value of $\alpha$ is . . . . . . . (Refractive index of water $= 4/3$)