Question

A lens with f= 10.0 cm is held

45.0 cm from an object. What is
the image distance?
(Unit = cm)
it is not 12 cm.

Answer 1

8.2 cm

Step-by-step explanation:

1/f = 1/so + 1/si

1/10 = 1/45 + 1/si

1/si = 1/10 - 1/45

1/si = 9/90 - 2/90

1/si = 7/90

si = 90/7 = 12.86 cm.

since you said that the answer was not 12 them the lens must be concave with negative (minus) focal length

1/f = 1/so + 1/si

- 1/10 = 1/45 + 1/si

1/si = - 1/10 - 1/45

1/si = -9/90 - 2/90

1/si = -11/90

si = -90/11 = - 8.2 cm

- (read: minus or negative sign) indicates the image is in the same side of the object

hope its true and can help you

Answer 2

1/f = 1/u + 1/v

f=10cm

u=45cm

v=? (Image distance)

1/v = 1/f - 1/u

1/v = 1/10 - 1/45

1/v = (9-2)÷ 90

1/v = 7/90

:. v = 90/7

v=12.86cm(image distance)