Use of "Have to"

What is the use of having more than pigment system molecule in a photocentre ?

What is the use of having two prongs of a tuning fork ? If one of the prongs is cut off, would the tuning fork be of any use ?

Correct Use of Would Have / Should Have / Could Have | SSC | IBPS PO | Railways

A parallel plate capacitor of area A, plate separation d and capacitance C is filled with three different dielectric materials having dielectric constants k_1 , k_2 and k_3 as shown. If a single dielectric material is to be used to have the same capacitance C in this capacitor, then its dielectic constant k is given by

A parallel plate capacitor of area A, plate separation d and capacitance C is filled with three different dielectric materials having dielectric constants k_1 k_2 and k_3 as shown in the following figure. If a single dielectric material is to be used to have the same capacitance C in this capacitor then its dielectric constant k is given by

A parallel plate capacitor of area A , plate separation d and capacitance C is filled with three different dielectric materials having dielectric constant K_(1),K_(2) and K_(3) as shown in fig. If a single dielectric material is to be used to have the same effective capacitance as the above combination then its dielectric constant K is given by :