what fraction of the maximum amplitude does the wave possess

1-Take a wave of Infrared radiation of wavelength 1.0 x 10-3 cm. If the amplitude of the wave = 0 at time t = 0 what fraction of the maximum amplitude does the wave possess at time t = 16.68 seconds?2-Radiation of wavelength 620 nm passes through 2 small slits that are 1 cm apart. Will waves that are diffracted by 60° in the same direction from the two slits completely reinforce each other? (Show calculations)3-Using Equation hn = 12mev2 I calculate the velocity of photoelectrons ejected from a sodiummetal surface with a work function of 2.46 eV by ultraviolet light of wavelength250 nm.