This is the 17711th most frequent Russian word.
удивитесь
"Удивитесь" means "you will be surprised" in English.
In this sentence, "удивитесь" is used in its literal sense, meaning 'you will be surprised' as an emotional reaction to discovering something new or unexpected.
Вы удивитесь, когда узнаете правду.
You will be surprised when you find out the truth.
Here, "удивитесь" is interrogative, exploring the possibility of the subject experiencing surprise; it reflects an expectation of a reaction.
Удивитесь ли вы, если это окажется правдой?
Will you be surprised if this turns out to be true?
In this example, "удивиться" is used in its imperative form, advising the subject to manage their emotional reaction to an upcoming revelation.