Questions in Ray Optics and Optical Instruments

Select	Question
	The relation between $n_1$ and $n_2$, if behaviour of light rays is as shown in figure is
	A candle placed 25 cm from a lens, forms an image on a screen placed 75 cm on the other end of the lens. The focal length and type of the lens should be
	We combined a convex lens of focal length $f_1$ and concave lens of focal lengths $f_2$ and their combined focal length was $F$. The combination of these lenses will behave like a concave lens, if
	In a plano-convex lens the radius of curvature of the convex lens is 10 cm. If the plane side is polished, then the focal length will be (Refractive index = 1.5)
	The focal length of a convex lens is 10 cm and its refractive index is 1.5. If the radius of curvature of one surface is 7.5 cm, the radius of curvature of the second surface will be
	A convex lens has a focal length $f$. It is cut into two parts along the dotted line as shown in the figure. The focal length of each part will be
	An object has image thrice of its original size when kept at 8 cm and 16 cm from a convex lens. Focal length of the lens is
	The combination of a convex lens ($f = 18 cm$) and a thin concave lens ($f = 9 cm$) is
	A convex lens forms a real image of an object for its two different positions on a screen. If height of the image in both the cases be 8 cm and 2 cm, then height of the object is
	A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are joined together. The power of the combination will be