What is parallax ?

In figure , L is half part of an equiconvex glass lens (mu=1.5) whose surfaces have radius of curvature R =40cm and its right surface is silvered . Normal to its principal axis a plane mirror M is placed on right of the lens . Distance between lens L and mirror M is b. A small object O is placed on left of the lens such that there is no parallax between final images formed by the lens and mirror. If transverse length of final image formed by lens is twice that of image formed by the mirror , calculate distance'a' in cm between lens and object.

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What can be the maximum distance of star which can be measured by using parallax method ?

Explain parallax method to measure distance between the earth and planet.

Why parallax method is not used for distance between star and earth which are at distance of 100 light year?

The principle of 'parallax' in section 2.3.1 is used in the determination of distances of very distant starts. The baseline AB is the line joining the Earth's two locations six months apart in its orbit around the Sun. That is, the baseline is about the diameter of the Earth's orbit = 3xx10^(11)m . However, even the nearest stars are so distant that with such a long baseline, they show parallax only of the order of 1" (second) of arc or so. A parsec is a conventent unit of length on the astronomical scale. It is the distance of an object that will show a parallax of 1" (second of arc) from opposite ends of a baseline equal to the distance from the Earth to the Sun. How much is a parsec in terms of metres ?

A man wishes to estimate the distance of a nearby tower from him. He stands at a point A in fron of the tower C and spots a very distant objct O in line with AC. He then walks pependicular to AC up to B, a distance of 100 m and look at O and C again. Since O is very distant the direction BO is practivally the same as AO, but he finds the line of slight by of C shifted fro the original line of slight by an angle theta=30^(@) (theta is known as parallax) estimate the distance of the tower C from his original position A.

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