EASY
Earn 100

A biconvex symmetrical lens made of glass of refractive index 1.56 has radii of curvature of magnitude 20 cm. Find the position of the image formed if an object is placed at a distance of 10 cm from this lens.

50% studentsanswered this correctly

Important Questions on Ray Optics and Optical Instruments

HARD
A thin convex lens is made of two materials with refractive indices n1 and n2, as shown in figure. The radius of curvature of the left and right spherical surfaces are equal. f is the focal length of the lens when n1=n2=n. The focal length is f+Δf when n1=n and n2=n+Δn. Assuming Δnn-1 and 1<n<2, the correct statement(s) is/are:
Question Image
EASY
A thin convex lens made from crown glass μ = 3 2  has focal length f . When it is measured in two different liquids having refractive indices 4 3  and 5 3 , it has the focal lengths f 1  and f 2  respectively. The correct relation between the focal lengths is :
EASY
Two similar thin equi-convex lenses of focal length f each are kept coaxially in contact with each other, such that the focal length of the combination is F1. When the space between the two lenses is filled with glycerin (which has the same refractive index (μ=1.5) as that of glass), then the equivalent focal length is F2. The ratio F1:F2 will be
MEDIUM

One plano-convex and one plano-concave lens of the same radius of curvature R but of different materials are joined side by side as shown in the figure. If the refractive index of the material of 1 is μ1 and that of 2 is μ2, then the focal length of the combination is:

Question Image

HARD
Sunlight of intensity 1.3 kW m-2 is incident normally on a thin convex lens of focal length 20 cm. Ignore the energy loss of light due to the lens and assume that the lens aperture size is much smaller than its focal length. The average intensity of light, in kW m-2 , at a distance 22 cm from the lens on the other side is __________.
HARD
A thin convex lens L (refractive index =1.5 ) is placed on a plane mirror M. When a pin is placed at A, such that OA=18 cm, its real inverted image is formed at A itself, as shown in figure. When liquid of refractive index μl is put between the lens and the mirror, the pin has to be moved to A', such that OA'=27cm, to get its inverted real image at A' itself. The value of μl will be

Question Image
MEDIUM
A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is 30 cm and the refractive index of the lens material is 1.5, then the focal length of the lens (in cm) is ___________.
EASY
The radius of curvature of the curved surface of a plano-convex lens is 10 cm. If the refractive index of the material of lens is 1.5, then it will ___.
HARD
A thin convex lens of focal length f is put on a plane mirror as shown in the figure. When an object is kept at a distance a from the lens-mirror combination, its image is formed at a distance a3 in front of the combination. The value of a is:
Question Image
MEDIUM
Two identical glass μg=32 equiconvex lenses of focal length, f are kept in contact. The space between the two lenses is filled with water μw=43. The focal length of the combination is
MEDIUM
A double convex lens has power P and same radii of curvature r of both the surfaces. The radius of curvature of a surface of a plano-convex lens made of the same material with power 1.5 P is :
MEDIUM
A plano - convex lens (focal length f2 , refractive index μ2, radius of curvature R) fits exactly into a plano - concave lens (focal length f1, refractive index μ1, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be:
EASY
Two thin lenses are in contact and the focal length of the combination is 80cm. If the focal length of one lens is 20cm, then the power of the other lens will be
HARD
Three glass cylinders of equal height H=30 cm and same refractive index n=1.5 are placed on a horizontal surface shown in figure. Cylinder I has a flat top, cylinder II has a convex top and cylinder III has a concave top. The radii of curvature of the two curved tops are same R=3 m. If H1,H2 and H3 are the apparent depths of a point X on the bottom of the three cylinders, respectively, the correct statement(s) is/are

Question Image
MEDIUM
A plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices μ1 and μ2,R is the radius of curvature of the curved surface of the lenses, then the focal length of combination is
EASY
A biconvex lens R1=R2=20 cm has focal length equal to focal length of concave mirror. The radius of curvature of concave mirror is [R.I. of glass lens =1.5]
MEDIUM
A convex lens is in contact with a concave lens. The magnitude of the ratio of their focal length is 53. If their equivalent focal length is 45 cm, the individual focal lengths of concave and convex lens are respectively.
HARD
The image of an object, formed by a plano - convex lens at a distance of 8 m behind the lens, is real and is one-third the size of the object. The wavelength of light inside the lens is   2 3  times the wavelength in free space. The radius of the curved surface of the lens is
EASY
A plano-convex lens of refractive index μ1 and focal length f1 is kept in contact with another plano-concave lens of refractive index μ2 and focal length f2. If the radius of curvature of their spherical faces is R each and f1=2f2, the μ1 and μ2 are related as:
EASY
Formation of real image using a biconvex lens is shown below:

Question Image

If the whole set up is immersed in water without disturbing the object and the screen positions, what will one observe on the screen?