Please answer all the four questions from the topic photoelectric effect.

The kinetic energies of photoelectrons range from zero to 4.0 x 10-1° J when light of wavelength 3000 A fals on a surface. What is the stopping potential for this light? What is the threshold wavelength for the materia The emitter in a photoclectric tube has a threshold wavelength of 6000 A. Determine the wavelength of the light incident on the tube if the stopping potential for this light is 2.5 V. Find the work function for potassium if the largest wavelength for electron emission in a photoelectric experiment is 5620 A.