71.

A narrow slit of width 2 mm is illuminated by monochromatic light of wavelength 500 nm. The distance between the first minima on either side on a screen at a distance of 1 m is

• 5 mm

• 0.5 mm

• 1 mm

• 10 mm

If e/m of electron is 1.76 x 10¹¹ C kg^-1 and the stopping potential is 0.71 V, then the maximum velocity of the photo-electron is

• 150 kms^-1

• 200 kms^-1

• 500 kms^-1

• 250 kms^-1