The least distance of distinct vision for a long-sighted person is x m. He wants to read a newspaper placed at a distance (x/2) m. The power of the spectacle lens used by him is x D What is the value of x ?

A person can see clearly only upto a distance of 25 cm . He wants to read a book placed at a distance of 50cm . What kind of lens does he require for his spectacles and what must be its power ?

A longsighted person has a minimum distance of distinct vision of 50 cm. He wants to reduce it to 25 cm. He should use a

L is a lens such that a parallel beam of light I ncident on it, after refraction, converges to a point at a distance x from it and M is a mirror such that a parallel lbeam of light incident on it, after reflection, converges to a point at a distance y from it. Now the lens L and mirror M are placed at a distan 2(x+y) from each other. An object of size 2 cm is kept infront of lens at a distance 2x from it. Find the nature, position , and size of the image that willl be seen by an observer looking toward the mirror through the lens.

A thin convex lens of focal length 30 cm is placed in front of a plane mirror. An object is placed at a distance x from the lens (not in between lens and mirror ) so that its final image coincides with itself. Then, the value of x is

For a certain lens, the magnification of an object when placed at a distance of 0.15 m is twice of the magnification produced, when the distance was 0.2 m. If in both the situations a real image is formed, then what is the focal length (in cm ) of the lens?

The two lenses of a compound microscope are of focal lengths 2 cm and 5 cm. If an object is placed at a distance of 2.1 cm from the objective of focal length 2 cm the final image forms at the final image forms at the least distance of distinct vision of a normal eye. Find the magnifying power of the microscope.

A telescope has an objective of focal length 50cm and an eyepiece of focal length 5cm. The least distance of distinct vision is 25cm. The telescope is focused for distinct vision on a scale 2m away from the objective. Calculate (a) magnification produced and (b) separation between objective and eyepiece.

The power of a lens used by short sighted person, is -2D. Find the maximum distance of an object which he can see without spectacles.

The ciliary muscles of eye control the curvature of the lens in the eye and hence can alter the effective focal length of the system. When the muscles are fully relaxed, the focal length is maximum. When the muscles are strained, the curvature of lens increases. That means radius of curvature decreases and focal length decreases. For a clear vision, the image must be on the retina. The image distance is therefore fixed for clear vision and it equals the distance of retina from eye lens. It is about 2.5cm for a grown up person. A perosn can theoretically have clear vision of an object situated at any large distance from the eye. The smallest distance at which a person can clearly see is related to minimum possible focal length. The ciliary muscles are most strained in this position. For an average grown up person, minimum distance of the object should be around 25cm. A person suffering from eye defects uses spectacles (eye glass). The function of lens of spectacles is to form the image of the objects within the range in which the person can see clearly. The image o the spectacle lens becomes object for the eye lens and whose image is formed on the retina. The number of spectacle lens used for th eremedy of eye defect is decided by the power fo the lens required and the number of spectacle lens is equal to the numerical value of the power of lens with sign. For example, if power of the lens required is +3D (converging lens of focal length 100//3cm ), then number of lens will be +3 . For all the calculations required, you can use the lens formula and lensmaker's formula. Assume that the eye lens is equiconvex lens. Neglect the distance between the eye lens and the spectacle lens. Q. A far sighted man connot see objects clearly unless they are at least 100cm from his eyes. The number of the spectacle lenses that will make his range of clear vision equal to an average grown up person will be

Displacement of a person moving from X to Y along a semicircular path of radius r is 200 m. What is the distance travelled by him ?