First of all Longitudinal waves is a matter in the medium that moves parallel to the direction of the wave travels.
1st example: sound travels parallel.
2nd example: when you talk you will here your voice again. because all the frequency bounce back to you.
In the other hand Transverse wave matter in the medium moves perpendicular to direction the wave travels.
For example: light is a good example of transverse wave.
Answer:
Δ L = 2.57 x 10⁻⁵ m
Explanation:
given,
cross sectional area = 1.6 m²
Mass of column = 26600 Kg
Elastic modulus, E = 5 x 10¹⁰ N/m²
height = 7.9 m
Weight of the column = 26600 x 9.8
= 260680 N
we know,
Young's modulus=
stress = 
= 
= 162925
strain = 
now,



Δ L = 2.57 x 10⁻⁵ m
The column is shortened by Δ L = 2.57 x 10⁻⁵ m
<span>the ratio of the velocity of light in the medium over the velocity of light in a vacuum</span>