Answer: 4.) 17.2cm
Explanation:
A flashlight is 40.0 cm from a double convex lens. The image of the flashlight is observed at a position 30.0 cm on the other side of the lens. What is the focal length?
Given the following :
Object distance(u) = 40cm
image distance (v) = 30cm
Focal length(f) =?
Using the mirror formular:
f = uv / (v+u)
f = (40 * 30) / (40 + 30)
f = 1200 / 70
f = 17.142857 cm
