Advertisements
Advertisements
Question
An equiconvex lens of focal length 'f' is cut into two identical plane convex lenses. How will the power of each part be related to the focal length of the original lens ?
Advertisements
Solution
\[\text{The focal length of original equiconvex lens is f } . \]
\[\text { Let the focal length of each part after cutting be F } . \]
\[\text { Here }, \]
\[\frac{1}{f} = \frac{1}{F} + \frac{1}{F}\]
\[ \Rightarrow \frac{1}{f} = \frac{2}{F}\]
\[ \Rightarrow f = \frac{F}{2}\]
\[ \Rightarrow F = 2f\]
\[\text { Power of each part will be given by }\]
\[P = \frac{1}{F}\]
\[ \Rightarrow P = \frac{1}{2f}\]
APPEARS IN
RELATED QUESTIONS
An object of size 3.0 cm is placed 14 cm in front of a concave lens of focal length 21 cm. Describe the image produced by the lens. What happens if the object is moved further away from the lens?
The image of a small electric bulb fixed on the wall of a room is to be obtained on the opposite wall 3 m away by means of a large convex lens. What is the maximum possible focal length of the lens required for the purpose?
Two converging lenses of unequal focal lengths can be used to reduce the aperture of a parallel beam of light without loosing the energy of the light. This increase the intensity. Describe how the converging lenses should be placed to do this.
Will the focal length of a lens for red light be more, same or less than that for blue light?
An unsymmetrical double convex thin lens forms the image of a point object on its axis. Will the position of the image change if the lens is reversed?
A plano convex lens has diameter of 10 cm and its thickness at the centre is 0.5 cm. Speed of light in the lens is 2 × 108 ms-1. What is the focal length of the lens?
In the given figure the radius of curvature of the curved face in the planoconvex and the planoconcave lens is 15 cm each. The refractive index of the material of the lenses is 1.5. Find the final position of the image formed.
The ratio of the height of the image to the height of the object is called:
According to the new Cartesian sign convention, all distances in lens problems are measured from:
A ray passing through the principal focus of a convex lens, after refraction, emerges:
