physics question !!!

Question

a convex lens has a focal length of 10 cm. an object 2 cm tall is placed in front of the lens.

(a) at what distance will the image appear inverted and 2 cm tall?

(b) at what object distance will the image appear erect and have a magnification of 3?

Answer 1

use 1/D_i+1/D₀=1/F ... with F= 10cm and h_i/h₀=-1 (-2/2) = Magnification = -D_i/D₀ (minus sign indicates inversion) thus D_i=D₀ and D_i=20cm=D₀

Answer 2

a) The magnification is -1 (inversion changes sign) m = -d_i/d_o so d_i = d_o (because d_i is positive, it is on the opposite side of the lens (where light rays can converge)

b) I leave this to you as the problem requires the same logic. m = +3_