A screen is placed 90, cm from an object. The | vedclass

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(B) The distance between the object and the screen is $D = 90\, cm$.The distance between the two positions of the convex lens is $d = 20\, cm$.The for

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$21.4$

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(B) The distance between the object and the screen is $D = 90\, cm$.The distance between the two positions of the convex lens is $d = 20\, cm$.The formula for the focal length $f$ of a convex lens in the displacement method is given by $f = \frac{D^2 - d^2}{4D}$.Substituting the given values into the formula:$f = \frac{(90)^2 - (20)^2}{4 	imes 90}$$f = \frac{8100 - 400}{360}$$f = \frac{7700}{360}$$f = \frac{770}{36} \approx 21.388\, cm$.Rounding to one decimal place,we get $f = 21.4\, cm$.

$A$ screen is placed $90\, cm$ from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by $20\, cm$. The focal length of the lens is.....$ cm$

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