Question

According to William Crookes experiments:
(A)- Cathode rays are deflected by the magnetic field
(B)- Anode rays are deflected by the magnetic field
(C)- Option A and B both are correct.
(D)- None of the above

Answer 1

William Crookes in his experiment with Crookes tube (which is also known as Crookes-Hittorf tube) was able to show that cathode rays are negatively charged. Cathode rays, also known as electron beams, are streams of electrons which are observed in discharge tubes.

Complete step by step answer:
- Let us first see the experimental Setup of William Crookes Experiment
(i) William took a discharge tube, a long glass tube, tightly sealed at both the ends properly and tightly fitted with 2 metal electrodes.
(ii) It has a side tube attached with a stopper cock that can be connected to a vacuum pump to decrease the pressure of the gas inside to any required value.
(iii) When a large voltage of approximate 10000 volts is applied between the electrodes then the following results are observed at various pressures :
(iv) When the pressure of the gas inside is 1 atmosphere then no current flows between the 2 electrodes.
(v) If the pressure is put down to about 10 millimetres,then-current starts flowing between
the 2 electrodes and thus a glow is viewed, the colour of the glow usually depends upon the nature of the gas taken into it.
(vi) If the pressure is decreased to 0.01 millimetre, then the glow between the
electrodes fade away but the current continues to flow and if a perforated anode is used, then a light faint greenish glow is seen on the glass walls behind the anode. This infers that few invisible rays are thus emitted from the cathode which passes through the holes of the anode and then hit the wall. These rays were known as cathode rays.

-Let us now see properties of cathode rays:
(i) They show a sharp shadow of the solid object obstructing their path. This infers that
cathode rays travel in a straight path.
(ii) If a lightweight paddle wheel stand on an axle is placed in their path, the wheel starts to
rotate. This indicates that cathode rays are constituents of material particles.
(iii) If an electric field is applied on cathode rays, then they are deflected towards the
positive plate of the electric field. This indicates that the cathode rays carry a negative charge.
(iv) When cathode rays hit on a metal foil, then the foil becomes hot. This shows that cathode rays produce heating effects.
(v) It produces green fluorescence on the glass walls of the discharge tube and also on certain other fluorescent substances such as zinc sulphide.
(vi) They possess penetrating effects and can easily pass through thin foils of metals.
The negatively charged particles constituting the cathode rays are called electrons.

So, the correct answer is “Option A”.

Note: Thus we can conclude that from the Crookes experiment that the cathode rays are negatively charged by observing the direction in which cathode rays are deflected by a magnetic field.