Sending an individual convicted of a crime to prison isn't a very effective way to deter crime. Prisons are good for punishing criminals and keeping them off the street, but prison sentences (particularly long sentences) are unlikely to deter future crime.
However, The fear of being caught and punished may deter people from committing crime. Deterrence can be individual or general. This uses punishment to deter an individual from reoffending. In most instances, people who believe they will be caught are less likely to commit crimes, that is, an appropriate level of punishment coupled with a high likelihood of being caught will likely deter some potential criminals. In essence, the punishment so imposed prevents others from committing the crime.