As a child, whenever you did something wrong, you invariably got punished for it. Sometimes the punishment wasn’t as severe as you had expected it to be; in fact, it turned out to be pretty mild. When you get slapped on the wrist for doing something wrong, you receive punishment which is not as severe as it might have been.
People who drive without a license shouldn’t get off with a slap on the wrist. They should be put in jail. *The children got a slap on the wrist for not doing their homework.
The expression `get your wrist slapped’ has the same meaning as `slap on the wrist’.
*We got our wrists slapped for not drinking the milk.
You normally hit someone on the back when you are proud of what he/she has done. The idiom `slap on the back’ is used to show approval. It has the same meaning as `pat on the back’.
*We should give Rahul a slap on the back for helping us organise the cultural programme.