Questions in Ray Optics and Optical Instruments

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	A concave lens of glass, refractive index $1.5$, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index $1.75$, it will behave as a
	A convex lens of focal length $0.5 m$ and concave lens of focal length $1 m$ are combined. The power of the resulting lens will be
	A double convex lens is made of glass of refractive index 1.5. If its focal length is 30 cm, then radius of curvature of each of its curved surface is
	A thin lens made of glass of refractive index 1.5 has a front surface + 11 D power and back surface – 6 D. If this lens is submerged in a liquid of refractive index 1.6, the resulting power of the lens is
	An object is placed first at infinity and then at 20 cm from the object side focal plane of the convex lens. The two images thus formed are 5 cm apart. The focal length of the lens is
	The distance between an object and the screen is 100 cm. A lens produces an image on the screen when placed at either of the positions 40 cm apart. The power of the lens is
	The image distance of an object placed 10 cm in front of a thin lens of focal length + 5 cm is
	A achromatic combination is made with a lens of focal length $f$ and dispersive power $\omega $ with a lens having dispersive power of $2\omega $. The focal length of second will be
	A biconvex lens with equal radii curvature has refractive index 1.6 and focal length 10 cm. Its radius of curvature will be
	A convex lens