Advertisements
Advertisements
प्रश्न
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
उत्तर
\[\text{The focal length of original equiconvex lens is f } . \]
\[\text { Let the focal length of each part after cutting be F } . \]
\[\text { Here }, \]
\[\frac{1}{f} = \frac{1}{F} + \frac{1}{F}\]
\[ \Rightarrow \frac{1}{f} = \frac{2}{F}\]
\[ \Rightarrow f = \frac{F}{2}\]
\[ \Rightarrow F = 2f\]
\[\text { Power of each part will be given by }\]
\[P = \frac{1}{F}\]
\[ \Rightarrow P = \frac{1}{2f}\]
APPEARS IN
संबंधित प्रश्न
- Determine the ‘effective focal length’ of the combination of the two lenses, if they are placed 8.0 cm apart with their principal axes coincident. Does the answer depend on which side of the combination a beam of parallel light is incident? Is the notion of the effective focal length of this system useful at all?
- An object 1.5 cm in size is placed on the side of the convex lens in the arrangement (a) above. The distance between the object and the convex lens is 40 cm. Determine the magnification produced by the two-lens system and the size of the image.
A man with normal near point (25 cm) reads a book with small print using a magnifying glass: a thin convex lens of focal length 5 cm.
(a) What is the closest and the farthest distance at which he should keep the lens from the page so that he can read the book when viewing through the magnifying glass?
(b) What is the maximum and the minimum angular magnification (magnifying power) possible using the above simple microscope?
A double convex lens of + 5 D is made of glass of refractive index 1.55 with both faces of equal radii of curvature. Find the value of its radius of curvature.
An object approaches a convergent lens from the left of the lens with a uniform speed 5 m/s and stops at the focus. The image ______.
In many experimental set-ups the source and screen are fixed at a distance say D and the lens is movable. Show that there are two positions for the lens for which an image is formed on the screen. Find the distance between these points and the ratio of the image sizes for these two points.
The point on the principal axis where rays parallel to the principal axis actually meet after refraction, or appear to diverge after refraction, is called the:
A ray of light passing through the optical centre of a thin lens:
A ray parallel to the principal axis, after refraction through a convex lens, passes through:
A ray parallel to the principal axis, after refraction through a concave lens, appears to diverge from:
Using the sign convention with \[OB = -u\] and \[DI = +v\] in the combined refraction equation for a thin lens gives:
