RAY OPTICS

A point object is placed at a distance of 20 cm from a thin planoconvex lens of focal length 15 cm. The plane surface is now silvered. The image created by the system is at

• 60 cm to the left of the system

• 60 cm to the right of the system

• 12 cm to the left of the system

• 12 cm to the left of the system

An extended object is placed at point O, 10 cm in front of a convex lens L1 and a concave lens L2 is placed 10 cm behind it, as shown in the figure. The radii of curvature of all the curved surfaces in both the lenses are 20 cm. The refractive index of both the lenses is 1.5. The total magnification of this lens system is

• 0.4

• 0.8

• 1.3

• 1.6

A point object is placed at the center of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is

• 2 cm

• 4 cm

• 6 cm

• 12 cm

A convex lens is in contact with a concave lens. The magnitude of the ratio of their focal lengths is 2/3 . Their equivalent focal length is 30 cm. What are their individual focal lengths?(in cm)

• -75,50

• -10,15

• 75,50

• -15,10

A biconvex lens is formed with two thin plano-convex lenses as shown in figure. Refractive index of left lens is 1.5 and that of right lens is 1.2. Both the curved surfaces are of same radius of curvature R=14 cm. For this bi-convex lens, for an object distance of 40 cm, the image distance (in cm) will be –

• -280.0

• 40.0

• 21.5

• 13.3

The diagram below show a light ray parallel to the principal axis of a spherical convex (diverging) mirror. Point F is the virtual focal point of the mirror and C is the centre of curvature. After the light ray is reflected, it will pass through point

• A

• C

• D

• F

You are asked to design a shaving mirror assuming that a person keeps it 10 cm from his face and views the magnified image of the face at the closest comfortable distance of 25 cm. The radius of curvature of the mirror would then be :

• -60 cm

• 24 cm

• 30 cm

• -24 cm

A plano–convex lens fits exactly into another plano-concave lens. Their plane surface are parallel to each other. If the lenses are made of different materials, what is the focal length of combination? Given that:

𝑅 = Radius of curvature of the curved portion

𝜇1 = refractive index of material of plano-concave lens

𝜇2= refractive index of material of plano-convex lens

An object of height 1 cm is kept at a distance of 40 cm from a concave spherical surface (R = 20 cm) separating air and glass (μ = 1.33). The location of the image formed is:

• - 32 cm

• + 16 cm

• -18 cm

• + 26 cm

An air bubble in a glass sphere of refractive index 1.5 is situated at a distance 3cm from a convex surface of diameter 10cm. At what distance from the surface will the bubble appear ?

• +2.5cm

• -3.5cm

• -2.5cm

• +3.5cm