What is the image distance of an object placed 10 cm from A convex lens having A focal length 15 cm?

A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the mircoscope have to be moved to focus on the needle again?

Case I: When tank is filled with water. Given, real depth = 12.5 cm;           apparent depth = 9.4 cm Now, using the formula, 

                    μ = real depthapparent depth

Refractive index,  μ = 12.59.4 = 1.33

Case II: When water in the tank is replaced by another liquid.

apparent depth = real depthμ 

i.e., apparent depth = 12.51.63 = 7.67 cm

Distance through which microscope has to be moved downward is = (9.4 – 7.67) cm = 1.73 cm.

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

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