Question

2. When an object is placed 6cm from a certain converging lens, it forms a real image. When the object is moved to 4cm from the lens, the image moves 1cm farther from the lens. Find the focal length of this lens.

Answer 1

so,

the object

u=-4

v=-1

1/f=1/v-1/u

1/f=1/-1-1/-4

1/f=-4+1/4

1/f=-3/4

f=-4/3