Rohit focused the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle , screen and lens as under : Position of candle = 26.0 cm Position of convex lens = 50.0 cm Position of screen = 74.0 cm i) What is the focal length of the convex lens? ii) Where will the image be formed if he shifts the candle towards the lens at a position of 38 cm? iii) Draw a ray diagram to show the formation of the image in case (ii) as said above?
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sorry iam doint this becoz i need pointa so i can ask my answers
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If the position of the candle is 26cm and the position of the convex lens is 50cm
Then the relative position of the cradle will be (50-26)cm=24cm
And the relative position of the screen will be (74-50)cm=24cm
Now acc to the lens formula:
1/f = 1/v-1/u
Therefore
1/f=v-u/vu
= 24-(-24)/-24*24. (Signs acc to sign convention)
=24+24/-576
=48/576
F=-576/48
=-12cm
Focal length is coming negative which is possible on only for concave lens and hence the question is wrong.
Then the relative position of the cradle will be (50-26)cm=24cm
And the relative position of the screen will be (74-50)cm=24cm
Now acc to the lens formula:
1/f = 1/v-1/u
Therefore
1/f=v-u/vu
= 24-(-24)/-24*24. (Signs acc to sign convention)
=24+24/-576
=48/576
F=-576/48
=-12cm
Focal length is coming negative which is possible on only for concave lens and hence the question is wrong.
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