The mean free path of the electrons is much longer than the length of the tube. Thus, the electrons, in general, do not collide in between, no ionization takes place and hence no light is emitted. The crookes dark space fills the entire tube and hence is 10cm long.
Answers & Comments
Let the mean free path be 'L' and pressure be 'P'
L∝1/p
for L= half of the tube length. P=0.02mm of Hg
As 'P' becomes half, 'L' doubles, that is the whole tube is filled with Crook's dark space.
Hence the required pressure
=0.02/2=0.01m of Hg.
Answer:
The mean free path of the electrons is much longer than the length of the tube. Thus, the electrons, in general, do not collide in between, no ionization takes place and hence no light is emitted. The crookes dark space fills the entire tube and hence is 10cm long.
Explanation: