In a compound microscope, the focal lengths of two lenses are 1.5 cm and 6.25 cm . An object is placed at 2 cm from objective and the final image is formed at 25 cm from eye lens. The distance between the two lenses is

Question

In a compound microscope, the focal lengths of two lenses are 1.5 cm and 6.25 cm . An object is placed at 2 cm from objective and the final image is formed at 25 cm from eye lens. The distance between the two lenses is, 6.00 c m, 7.75 c m, 9.25 c m, 11.00 c m

MARKS App · Accepted Answer

f 0 = 1.5 cm , ⁡ f e = 6.25 cm , ⁡ u 0 = - D = - 25 c m By objective lens 1 f 0 = 1 v 0 - 1 u 0 1 1.5 = 1 v 0 - 1 - 2 ⇒ 1 v 0 = 1 1.5 - 1 2 or v 0 = 6 c m By eyepiece 1 f e = 1 v e - 1 u e 1 6.25 = 1 - 25 - 1 - u e ⇒ 1 u e = 1 6.25 + 1 25 ⇒ 1 u e = 4 25 + 1 25 = 1 5 ⇒ 1 u e = 1 5 u e = 5 c m , Length of tube = L = v o + u e = 6.0 + 5.0 = 11 c m

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