Choose the correct relation between `l_(1)` and `l_(2)` ?

What is the relation between l and m_(l) ?

The masses and length of two simple pendulums are given as respectively m_(A), m_(B), L_(A) and L_(B) . If frequency of A is double that of B then relation between L_(A) and l_(B) is given as

L_(1) is the length between two adjacent carbon atoms in a layer and L_(2) is the length in-between two layers of graphite. The approximate ratio between L_(1) and L_(2)

Your are given three lenses L_(1), L_(2) and L_(3) each of focal length 20cm. An object is kept at 40cm in front of L_(1) as shown. The final real image is formed at the focus I of L_(3) . Find the separation between L_(1) and L_(2) and L_(3) .

L_(1) is the length between two adjacent carbon atoms in a layer and L_(2) is the length in between two layers of graphite. The approximate ratio between L_(1) " and " L_(2) is