Question

(iii) The atomic number of aluminium is 13. With the help of
diagram, write the electronic configuration and valency.
5
Shell
to
... The valency of aluminium =
(iv) Explain how dew and fog are formed.
(v) Two convex lenses of equal focal lengths are kept in contact
with each other. If the power of their combination is 20 D.
find the focal length of each convex lens.​

Answer 1

Answer:

(iii) Electronic Configuration: K(2), L(8), M(3)

Valency: +3

(v) ATQ: P=20D

as, f₁=f₂

Thus, P₁=P₂

=>P₁+P₂=20

=>2P₁=2P₂=20

P₁=P₂=10D