37) If the wavelength of light falling on a surface is increased from 3000?A⁰?to 3040?A⁰, then what will be the corresponding change in the stopping potential (given that hc = 12.4?10⁷?eV?)?

38) If the wavelength of light incident on photo-electric cell be reduced from 4000A⁰?to3600A⁰,then what will be the change in the cut off potential.

39) If the voltage across the electrodes of a cathode ray tube is 500 volts then energy gained by the electrons is

40) Which of the following is correct about photoelectric cell?

41) If a beam goes undeflected in Thomson's experiment, then speed of the electron is