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

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 statement is not correct?

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

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