The peak emission from a black body at a certain temperature occurs at a wavelength of 9000Å. On increasing its temperature the total radiation emitted is increased 81 times. At the initial temperature when the peak radiation from the black body is incident on a metal surface it does not cause any photoemission from the surface. After the increase of temperature the peak radiation from the black body caused photoemission. To bring these photoelectrons to rest, a potential equivalent to the excitation energy between the n = 2 to n = 3 Bohr levels of hydrogen atom is required. Then answer the following questions.

(i) Stopping potential for the photoelectrons emitted by peak radiation is –