Why iddah is longer for widow?

Reason for iddat

Why Long iddat for widow? 

Read following article for information

https://islamqa.info/en/answers/132479/the-reason-why-the-%60iddah-of-a-woman-whose-husband-has-died-is-longer-than-that-of-a-woman-who-has-been-divorced

Pregnancy and iddat

Iddat for divorcee

Iddat acknowledgement of husband's favours

Faithfulness and divorce

Iddat during ignorance period

Cleaning and wearing clothes are allowed during iddah ( after death of husband)

 https://islamqa.info/en/answers/132479/the-reason-why-the-%60iddah-of-a-woman-whose-husband-has-died-is-longer-than-that-of-a-woman-who-has-been-divorced