The distance between an object and a screen is 100 cm. A lens can produce real image of the object on the screen for two different positions between the screen and the object. The distance between these two positions is 40 cm. If the power of the lens is close to 100 N D where N is an integer, the value of N i $s________.$
Options

Question

The distance between an object and a screen is 100 cm. A lens can produce real image of the object on the screen for two different positions between the screen and the object. The distance between these two positions is 40 cm. If the power of the lens is close to 100 N D where N is an integer, the value of N i $s________.$

Options

G1 Physics · Accepted Answer

Derived solution: Step 1: Use the thin-lens formula 1/f = 1/v - 1/u with m = v/u. For lens material/medium changes use the lens-maker relation with the relative refractive index; powers of thin lenses in contact add. Step 2: Substitute the values given in the question and apply the geometry/sign convention shown. Step 3: On simplification the result is 476. Therefore the correct option is B.