A photo cell is illuminated by a small bright source placed at 1m away. When the same source of light is placed 2m away, which of the following is true about the electrons emitted by the photo cathode?

Number of photo electrons is directly proportional to solid angle ϕ. Since distance d is large compared to the size of the metal surface we can write  ϕ=Ad2 where A is the area of target metal. Hence n∝1d2 where n is the number of free electrons. ∴ n1n=dd12=d2d2=14