Three lenses of forcal lengths +10 , -10 cm and +30 cm are placed at distance of 30 cm , 35 cm and 45 cm respectively from an object.
The distance between the object and the image formed is

Options

A. 100 cm
B. 75 cm
C. 30 cm
D. 45 cm

Answer

B

Explanation

Three lenses of focal length 10,-10 and 30 cm is given in figure ,

Now using lens formula, distance of image from lens A
`1/(V_A) -1/(u_A) =1/(f_A) rArr 1/(V_A) -1/(-30)=1/(+10) rArr V_A =+ 15 cm `
Similarly, distance of image from lens B ,
`1/(V_B)-1/(+10)=-1/(10) rArr V_B = oo`
Distance of image from lens C.
`1/(V_c)-1/(oo)=1/(30) rArr V_c = +30 cm`
Hence, the total distance between object and image,
`d_T = d_(0C) +V_C =(30 _45) cm = 75 cm `