Question

A real, light emitting object is 15 cm to the left of a lens with a focal length of 10 cm. Where is the image? Please explain

Part B- A real, light emitting object is 15 cm to the left of a lens with a focal length of ?10 cm. Where is the image? I am getting conflicting answers from people please show work

Answer 1

a) focal length positive

now use lens makers formula

1/ v + 1/u = 1/f

v = image distance =?

u = object distance = 15 cm

f = focal length = 10 cm

1/v + 1/15 = 1/10

v = 30 cm (since it comes +ve so image will be right side of the lens).

b)  focal length negative

now use lens makers formula

1/ v + 1/u = 1/f

v = image distance =?

u = object distance = 15 cm

f = focal length = - 10 cm

1/v + 1/15 = - 1/10

v = - 6 cm (since it comes -ve so image will be left side of the lens).