Home
Class 10
PHYSICS
Two convex lenses of equal focal lengths...

Two convex lenses of equal focal lengths are kept in contact with each other. If the power of their combination is 20 D, find the focal length of each convex lens.

Text Solution

Verified by Experts

The focal length (f) of the combination of the lenses is given by
` 1/f = 1/f_(1) + 1/f_(2)`
` therefore 1/f = 1/f_(1) + 1/f_(1) = 2/f_(1)`
But ` P = 1/f therefore P = 2/f_(1) " " therefore D = 2/f_(1) " " therefore f_(1) = 2/20 m = 0.1 m`
This gives the focal length of each convex lens.
Promotional Banner

Topper's Solved these Questions

  • NUMERICAL EXAMPLES

    NAVNEET PUBLICATION - MAHARASHTRA BOARD|Exercise Space Missions|5 Videos

  • NUMERICAL EXAMPLES

    NAVNEET PUBLICATION - MAHARASHTRA BOARD|Exercise Examples for Practice|22 Videos

  • NUMERICAL EXAMPLES

    NAVNEET PUBLICATION - MAHARASHTRA BOARD|Exercise Refraction of Light|4 Videos

  • NAME THE FOLLOWING/WRITE THE CHEMICAL FORMULA/ELECTRONIC CONFIGURATION

    NAVNEET PUBLICATION - MAHARASHTRA BOARD|Exercise Lenses|7 Videos

  • PARAGRAPH BASED QUESTIONS

    NAVNEET PUBLICATION - MAHARASHTRA BOARD|Exercise LENSES|5 Videos

Similar Questions

Explore conceptually related problems

Two convex lenses of equal focal lengths are kept in contact with each other. If the power of their combination is 10D , find the focal length of each convex lens.

Two concave lenses, eacb of focal length 30 cm are placed in contact with each other. Find the power of the combination.

Three lenses lenses of focal length 20 cm each are kept in contact with each other . Find the power of their combination.

A concave lens of focal length 25 cm and a convex lens of focal length 20 cm are placed in contact with eachother. What is the power of this combination ? Also, calculate focal length of the combination.

Two thin convex lenses of focal lengths f_(1) and f_(2) are in contact and coaxial. The power of the combination is

Two convex lenses of focal lengths 25 cm and 15 cm are placed in contact with each other. Find the focal length of combination.

If two convex lenses of focal lengths 10 cm and 5 cm are kept in contact with each other , what is their combined focal length ?

Two lenses of power -15D and +5 D are in contact with each other. The focal length of the combination is