The passive is used in the following circumstances:
1. The originator {doer) of the action is considered less important than the action itself. In other words, when the action is to be given more importance or is to be highlighted, we use passive voice.
2. We do not want to identify the originator (doer) of the action eg, (in the sentence Oranges are grown in Morocco.)
3. It is not necessary, relevant and not helpful to mention the originator {doer) of the action. For example, in the headline Terrorists Arrested mentioning the Police is irrelevant as it is implied or understood.
This is especially useful when we want to be brief and eyecatching as in headlines, and notices etc.
4. We have to be more objective in a statement. For example, instead of saying ‘I think the Taj Mahal is the most beautiful mausoleum in the world’ we suggest (in not writing ‘I think’) that it is generally thought to be so. This is effectively done in shifting from a subjective view (T think’) to the objective one by not adding ‘I think’.
5. We are writing in a formal and academic style eg, reports of scientific experiments or of meetings etc. In writing these, the emphasis is merely on the facts etc. Therefore, these are to be as neutral and objective as possible. Repeating or mentioning the originator or the doer in them would look foolish.’
6. It is not known about the originator or the doer of the action eg, when a crime has been committed.
7. We want to describe events and actions from a single point of view eg, the report of Inspector Narayan.
(b) The other times when the passive is used are when a commentary is broadcast eg, of the Republic Day Parade etc.
