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In u-v method, we require the distance b...

In `u-v` method, we require the distance between object or image from the pole (vertex) of the mirror (actual distance). But practically we measure the distance between the indices `A` and `B`. (Observed distance). Which need not exactly co-inside with object and pole, there can be a slight mismatch called index error, which will be constant for every observation.

Index error=Observed distance-Actual distance(Just like zero error in screw guage, it is the excess reading).
To determine index error, mirror and object needle and placed at arbitary position. For measuring actual distance, a knitting needle is just fitted between the pole of mirror and object needle `O`. The length of knitting needle will give the actual object distance while the seperation between indices `A` and `B` at that instant is the observed distance.
So index error is-
`e=`Observed distance-Actual distance
`=` Separation between indices `A` and `B`- Length of knitting neddle once we get `e`, in
every observation, we get
Actual distance=Observed distance (separation between the indices)- Excess reading(e) There is an another term, Index corraction which is invert of index error.
Index correction=-index error
To find index error for `u`, when a knitting needle of length `20.0cm` is adjusted between pole and object needle, the sepertion between the indices of object needle and mirror was observed to be `20.2cm`. Index corraction for u is

A

`-0.2cm`

B

`0.2cm`

C

`-0.1cm`

D

`0.1cm`

Text Solution

Verified by Experts

The correct Answer is:
B
Index error(excess reading)=Observed reading-Actual reading
`=20.2-20.0=0.2cm`
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In u-v method, we require the distance between object or image from the pole (vertex) of the mirror (actual distance). But practically we measure the distance between the indices A and B . (Observed distance). Which need not exactly co-inside with object and pole, there can be a slight mismatch called index error, which will be constant for every observation. Index error=Observed distance-Actual distance(Just like zero error in screw guage, it is the excess reading). To determine index error, mirror and object needle and placed at arbitary position. For measuring actual distance, a knitting needle is just fitted between the pole of mirror and object needle O . The length of knitting needle will give the actual object distance while the seperation between indices A and B at that instant is the observed distance. So index error is- e= Observed distance-Actual distance = Separation between indices A and B - Length of knitting neddle once we get e , in every observation, we get Actual distance=Observed distance (separation between the indices)- Excess reading(e) There is an another term, Index corraction which is invert of index error. Index correction=-index error To find index error for v , when the same knitting needle is adjusted between the pole and the image needle, the separation between the indices of image needle and mirror was found to be 19.9cm . Index error for v is

To find index error for u when a knitting needle of length 20.0cm is adjusted between pole and object needle the separation between the indices of object needle and mirror was pbserved to be 20.2 cm Index correction for u is .

In u-v method, we require the distance between object or image from the pole (vertex) of the mirror (actual distance). But practically we measure the distance between the indices A and B . (Observed distance). Which need not exactly co-inside with object and pole, there can be a slight mismatch called index error, which will be constant for every observation. Index error=Observed distance-Actual distance(Just like zero error in screw guage, it is the excess reading). To determine index error, mirror and object needle and placed at arbitary position. For measuring actual distance, a knitting needle is just fitted between the pole of mirror and object needle O . The length of knitting needle will give the actual object distance while the seperation between indices A and B at that instant is the observed distance. So index error is- e= Observed distance-Actual distance = Separation between indices A and B - Length of knitting neddle once we get e , in every observation, we get Actual distance=Observed distance (separation between the indices)- Excess reading(e) There is an another term, Index corraction which is invert of index error. Index correction=-index error In some observation, the observed object distance (Separation between indices of object needle and mirror) is 30.2cm , and the observed image distance is 19.9cm . Using index correction from previous two equations, estimate the focal distance of the concave mirror!

To find index error v when the same knitting needle is adjusted between the pole and the image needle the separation between the indices of image needle and mirror was found to be 19.9 cm Index error for v is .

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