To find the focal length of concave lens using convex lens | Physics Practical Class 12 | Gaurav Kumar

 To find the focal length of concave lens using convex lens.

Aim: -

To find the focal length of concave lens using convex lens.

APPARATUS: -

Optical bench four uprights, concave lens, convex lens, two pins, two lens holder.

THEORY: -

OBSERVATION: -

1.    Rough focal length of the convex lens =    .................... cm

2.    Length of the knitting needle    (x)        =    ................... cm

3.    Observed distance between L2 and I (y)    =    .............. cm

4.    Index correction for u and v both              =    x - y     =     ............. cm

TABLE: Determination of focal length

CALCULATIONS: - 

Using 

 calculate f for each pair of u and v and then find mean f.

RESULT: -

The focal length of the given concave lens. By using convex lens is ........ cm.

PRECAUTIONS: -

1.    Focal length of the convex lens should be less than the focal length of concave lens so that the combination behaves as convex.

2.    The tips of the needles and the center of the lens should be at the same height.

3.    Parallax must be removed tip to tip.

4.    The index correction should be taken into account.

5.    The uprights carrying the lens and the needles should not be shaky.