To form an achromatic combination, two lenses of focal length X and Y and dispersive power A and B respectively, are kept in contact. Which of the following is correct?

In a glass ($\mu =1.5$) sphere of radius 10 cm, there is an air bubble B at distance 5 cm from C. The distance of bubble from the surface of the sphere (i.e. point A) as observed from point P in the air will be

A concave lens is made of three layers of glass of three different materials as shown in the furure. A point object is placed on its axis. Number of images of the object is -

An object is placed at a distance of 20 cm from the thin lens as shown in the figure. The points $C_1$ and $C_2$ denote centres of curvature. The magnification produced by the lens is (Refractive index of glass is 1.5)

A lens forms image of a point object placed at distance 20 cm from it, just in front of the object at distance 4 cm from the object towards the lens. The power of lens is

A point object O is placed on the principal axis of the convex lens of focal length f = 20 cm at a distance of 40 cm. The diameter of the lens is 10 cm. An eye is placed 60 cm to the right of lens and a distance h below the principal axis. The maximum value of h to see the image is-

If a glass prism of refractive index 1.5 dipped in a liquid having refractive index same as that of the material of prism, then the dispersive power of prism will

If the wavelength of a ray of light from a source of lights is 3000 $\stackrel{0}{A}$in air, then the wavelength of that ray of light in a liquid in which S is placed will be:

Chromatic aberration is absent in

For a convex lens of focal length 15 cm the dispersive power of its material is 0.05. The longitudinal chromatic aberration of the lens is

A convex mirror of a focal length f (in air) is immersed in water $\left(\mu =\frac{4}{3}\right)$. Focal length of the mirror in water will be

A plane mirror is placed on x-z plane and is free to rotate about z-axis. A fixed object in on x-y plane at a point O(5m, 5m). When mirror starts rotating anticlockwise with angular speed 5 rad/s about z-axis. The initial linear speed of image is

An object is placed at infinite distance from a concave lens. If m is magnification obtained in the size of the image; then

A point object O is placed at distance 20 cm from a biconvex lens of radius of curvature 20 cm and $\mu$=1.5. The final image produced by lens and mirror combination will be at

If the angle of a triangular prism is A and the refractive index of the material is $\mu$, then under what condition will there be no emergent ray?

A thin lens whose power is +2D is cut into two pieces perpendicular to the principal axis. The focal length of each part will be

A light ray is incident at an angle of $60°$ on one face of a  prism of a refractive angle $90°$. If light ray grazes the second face, then the refractive index of the material of prism is-

The near point of a hypermetropic eye is 1m. What is the power of the lens required to correct this defect?

The minimum magnifying power of an astronomical telescope is 40. If the length of the telescope is 205 cm, then the focal length of its field lens is

A boy with defective eye-sight cannot see things beyond 50cm. The corrective lens required has the power

The focal lengths of the objective and eyepiece of a terrestrial telescope are 50 cm and 10 cm respectively. The magnifying power of the telescope when the final image is formed at infinity is

A convex mirror of focal length 20 cm forms image which is quarter the size of the object. The distance of the object from the mirror is

The focal length of a thin convex lens for red and blue light is 0.5m and 0.484m.  The dispersive power of the lens is 

What is the length of the optical path of two media in contact having thickness 2 cm and 3 cm and refractive indices 1.5 and 1.7 respectively?

Two thin convex lenses of focal length 20cm and 5cm are placed 10cm apart. The power of the combination of lenses is 

A converging beam of light forms a point image on a screen of an object. A plane glass plate of thickness 2 cm and a refractive index $\frac{3}{2}$ is introduced in the path of the beam. The screen should be shifted with respect to its initial position to obtain point image on the screen will be

Select the incorrect option

The refractive index of the material of an equilateral prism for yellow light is 1.5. The angle of minimum deviation of the prism for yellow light is (sin $49°$ = 0.75)

In case of a compound microscope, the image formed by the objective lens is

A plano-convex lens of focal length 10 cm is made of glass of refractive index 1.5. If the plane surface of the convex lens is polished, then the focal length of the resultant combination will be