How to find focal length of concave lens using convex lens?
Answers
To determine rough focal length of convex lens
Mount the convex lens in lens holder.
Go out in the open and face the lens towards distant tree or building.
Obtain the image of the tree or the building on a white painted wall (screen) and move the lens forward and backward to get a sharp image on the wall.
Measure the distance between the lens and the wall (screen). This will be equal to the rough focal length of the mirror.
To set the convex lens
Follow steps 2 to 4 of Experiment 2 To set the object needle
Follow steps 5 to 8 of Experiment 2 To set the image needle at I
Follow steps 21 to 27 of Experiment 2 To set the concave lens
Clamp the holder with concave lens on fixed upright on the I side of the convex lens.
Fix this upright at some distance away from the convex lens.
Set the concave lens surface in same manner as convex lens surface with principal axes of the lenses coinciding.
Answer:
Any incident ray traveling parallel to the principal axis of a converging lens will refract through the lens and travel through the focal point on the opposite side of the lens. ... These rays of light will refract when they enter the lens and refract when they leave the lens.