would have

I don't understand the question. The form 'would have' does not depend on what follows it.

as par rule after would have, we used past participial, but here does't seem. beacuse after would have there is noun "effect of a subtle altering of the way "

You are confusing the auxiliary verb and the main verb:

Auxiliary: I have worked, I will have worked, I would have worked, etc.
Main It has an effect, it will have an effect, it would have an effect, etc

"Would have" can take an object:

The would have meat at every meal, if they could afford it.

Pl. explain in details, because i never saw "the would have" in my grammar study.

thanks.

it's like there's a missing part of the sentence and it should be a conditional sentence for example in your sentence it could have been "
If something happened that would have the effect..." it's like the first part of the sentence is omitted because it was mentioned before,somewhere in the context

maskarvaibhavPl. explain in details, because i never saw "the would have" in my grammar study.thanks.

She made a typing error. "They would have ...."

maskarvaibhavPl. explain in details, because i never saw "the would have" in my grammar study.thanks.

Have you studied modal verbs yet?

Modal verbs are not inflected.
They are used with the infinitive form of another (main) verb.
Would is one of the modal verbs. It has many uses.

I would like an ice cream. (polite request)