When to use "такой", "какой" or "так" respectively for emphasis?

Question

I'm a bit fuzzy on the usage of these three words -- specifically when they are used for emphasis in the sense of "so much / such".

How are these two nuanced:

1) Такая жара! {vs} Какая жара!

Is it impossible to say "Он так яркий, что ..." here:

2) Он такой яркий, что я не могу на него смотреть.

For the emphatic meaning of "How + (adjective/adverb) !" in English, can only "какой" be used:

3) Какой обидчивый. = How touchy.

Why is it impossible to say "Такое плохо?" here:

4) Так плохо? = Is it that bad?

Answer 1

1. As for emphatic sentences, to my mind there isn't much difference in the following

Такая жара! (Such hot weather we are having!)

Какая жара! (What hot weather we are having!)

2 Он такой яркий, что я не могу на него смотреть.

We have an adjective in the full form, so for the emphasis use the full form of "такой". Though It's impossible to use "так" to emphasize a full adjective, you can use it before a short form, but you can't use "такой" here.

Он так ярок, что я не могу на него смотреть.

3 For the emphatic meaning of "How + (adjective/adverb) !" in English, can only "какой" be used?

It depends on what exactly comes after "how", in case it is a full adjective, you use "какой"

Какой обидчивый!= How touchy.

If you have a short adjective, use "как"

Посмотрите, как (он ) обидчив!

If you have an adverb, also use "как", "так".

Как плохо! Так плохо?

"Плохо" is an adverb. Not a noun, so "какое"and "такое" are impossible.

Такое/какое can be used either with full adjectives or nouns in the neutral gender.

Какое/такое горе! Какое/такое огромное!

Ask the last question separately , because it has nothing to do with the emphasis.