Home
Class 12
PHYSICS
Two identical glass (mu(g)=3//2) equi- c...

Two identical glass `(mu_(g)=3//2)` equi- convex lenses of focal length f each are kept in contact. The space between the two lenses is also filled with water `(mu_(g)=4//3).` The focal length of the combination is

A

f/3

B

f

C

`(4f)/(3)`

D

`(3f)/(4)`

Text Solution

Verified by Experts

The correct Answer is:
D
(d) Consider the situtation shown in figure. Let radius of curvature of the lens surfaces is R. The combination is equivalent to three lenses is contact

`therefore 1/(f_(eq))=1/(f_(1))+1/(f_(2))+1/(f_(3))=2/(f_(1))+1/(f_(2))(becausef_(1)=f_(3))`
Now, `1/(f_(1))=1/(f_(3))=(mu-1)(2/R)=1/f`
`1/(f_(2))=(u_(w)-1)(-2/R)=(4/3-1)((-2)/R)`
`=(1/3)(-2/R)=((-2)/3)(1/(2(mu-1)))1/f`
`rArr1/(f_(2))=(-1/3)(1/(3/2-1))(1/f)=-2/3xx1/f`
`therefore1/(f_(eq))=2/f-2/3xx1/f=(6-2)/(3f)=4/(3f)`
`rArr` The focal length of the combination, `f_(eq)=(3f)/4`
Doubtnut Promotions Banner Mobile Dark
|

Topper's Solved these Questions

  • RAY OPTICS

    DC PANDEY|Exercise medical entrance special format question|25 Videos

  • NUCLEI

    DC PANDEY|Exercise C MADICAL ENTRANCES GALLERY|46 Videos

  • REFLECTION OF LIGHT

    DC PANDEY|Exercise Subjective|9 Videos

Similar Questions

Explore conceptually related problems

Two identical glass (mu_(g)=3//2) equiconvex lenses

Two identical equiconvex lenses of refractive index 3//2 and focal length 16 cm are kept in contact. The space between the lenses is filled with water of refractive index 4//3 . What is the focal length of the combination ?

Knowledge Check

  • Two identical glass (mu_(g)=3//2) equi- convex lenses of focal length f each are kept in contact. The space between the two lenses aiisolfilled with water (mu_(g)=4//3). The focal length of the combination is

    A
    `f//3`
    B
    `f`
    C
    `(4f)/3`
    D
    `(3f)/4`

  • Two identical glass (mu_(g) = 3//2) equiconvex lenses of focal length f each are kept in contact. The space between the two lenses is filled with water (mu_(w) = 4//3) . The focal length of the combination is :-

    A
    `4f//3`
    B
    `3f//4`
    C
    `f//3`
    D
    `f`

  • Two identical glass (mu_(g)=3//2) equiconvex lenses of focal length f are kept ini contact. The space between the two lenses is filled with water (mu_(w)=4//3) . The focal length of the combination is

    A
    `f`
    B
    `(f)/(2)`
    C
    `(4f)/(3)`
    D
    `(3f)/(4)`

    • Similar Questions

    Explore conceptually related problems

    Two concave lenses each of focal length 30 cm are placed in contact. What is focal of the compound lens ?

    Two identical glass (mu_(g)=3//2) equiconvex lenses of focal length f are kept in contact. The space between the two lenses is filled with water (mu_(w)=4//3) . The focal length of the combination is

    Two concave lenses L_1 and L_2 are kept in contact with each other. If the space between the two lenses is filled with a material of smaller refractive index, the magnitude of the focal length of the combination

    Two lenses of power 15D and -3D are placed in contact. The focal length of the combination is a

    Two equi convex lenses each of focal lengths 20 cm and refractive index 1.5 are placed in & contact and space between them is filled with water of refractive index 4/3 . The combination works as

    Home
    Profile