Ray Optics Test...

Two similar plano-convex lenses are combined together in three different ways as shown in the adjoining figure. The ratio of the focal lengths in three cases will be

Two lenses of power +12 and –2 dioptres are placed in contact. What will the focal length of combination?

A concave and convex lens have the same focal length of 20 cm and are put into contact to form a lens combination. The combination is used to view an object of 5 cm length kept at 20 cm from the lens combination. As compared to the object, the image will be

If in a plano-convex lens, the radius of curvature of the convex surface is 10 cm and the focal length of the lens is 30 cm, then the refractive index of the material of lens will be

The slit of a collimator is illuminated by a source as shown in the adjoining figures. The distance between the slit S and the collimating lens L is equal to the focal length of the lens. The correct direction of the emergent beam will be as shown in figure

A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen

A glass convex lens (µ_g = 1.5) has a focal length of 8 cm when placed in air. What would be the focal length of the lens when it is immersed in water (µ_w = 1.33)?

If I₁ and I₂ be the size of the images respectively for the two positions of lens in the displacement method, then the size of the object is given by

A biconvex lens forms a real image of an object placed perpendicular to its principal axis. Suppose the radii of curvature of the lens tend to infinity. Then, the image would

The radius of curvature of convex surface of a thin plano convex lens is 15 cm and refractive index of its material is 1.6. The power of the lens will be