A simple microscope is a combination of two lenses in contact. Their powers are +20 D and -4 D . The distance of distinct vision is 25 cm . When seen through the microscope, the size of the image of an object 3 mm high is

Step-by-step solution

The equivalent power of the lens combination is given by the sum of their individual powers: P = P₁ + P₂ = +20 D - 4 D = +16 D The focal length of the combination is: f = 1 P = 1 16 m = 100 16 cm = 6.25 cm For a simple microscope, when the image is formed at the least distance of distinct vision ( D = 25 cm ), the linear magnification m is given by: m = 1 + D f Substituting the values: m = 1 + 25 6.25 = 1 + 4 = 5 The size of the image h_i is the magnification times the size of the object h_o : h_i = m h_o = 5 3 mm