What is the image distance of a 4 cm tall object placed 40 cm from a concave mirror having a focal length of 10 cm?

Choose one answer.
a. -13.3 cm
b. 13.3 cm
c. -40.0 cm
d. 40.0 cm

3 answers

f = 10 c,

!/Do + !/Di = 1/f

Di is the object distance.

1/40 + 1/Di = 1/f

1/Di = 1/f - 1/Di = 1/10 - 1/40 = 3/40

Di = ___ cm

The object height (4 cm) does not matter when location image location.
1/f=1/v+1/u
where f=focal length
v=image distance
u=object distance
1/10=1/v+1/40
1/10-1/40=3/40
3/40=1/v cross multiply
3v/3=40/3 divide both sides by 3
v=13.3 cm
suppose you place a 5.0cm tall spring in front of a concave mirror. the mirror has a focal length of 24cm. the spring forms an image that appears to be at the same position as the spring,but the image is inverted. where did you place the spring? how tall is the springs image?