Which one of the following statements is not correct for light rays ?

Which one of the following statement is not correct?

Which of the following statement is not correct?

Which one of the following statements about the aperture of a convex lens is correct?

Which one of the following statements is correct regarding the travel of a light beam from a rare to a dense medium?

Raman effect is due to Sir C. V. Raman. Which of the following statements is correct about 'Raman effect?