In photoelectric effect, kinetic energy of emitted photoelectrons is directly proportional to the frequency of emitted photoelectrons. Hence, on increasing frequency of incident radiation, kinetic energy of emitted photoelectron increases. Hence, statement I is incorrect and statement IV is correct. In photoelectric effect, photoelectric emission takes place only when frequency of incident radiation is greater than or equal to threshold frequency, no matter how much intensity of incident light is. Hence, statement II is not correct. In photoelectric emission, maximum kinetic energy of emitted photoelectrons depends only frequency of inçident radiation and does not depend on intensity of incident radiation. Hence, statement III is correct.