Question

A stream of charged particles enter into a region with crossed electric and magnetic fields as shown in the figure below. On the other side is a screen with a hole that is right on the original path of the particles

Then

• A. no particle can get through the hole
• B. all particles can get through the hole
• C. only positively charged particles with speed $\frac{E}{B}$ can get through the hole
• D. all particles with speed $\frac{E}{B}$ can get through the hole

Answer 1

Answer: (A)

Direction of force on positive charged particle by Fleming’s left hand rule is towards direction of electric field.

As, electric force on positively charged particle is also in same direction.
So, a positively charged particle will be deflected upwards.
Hence, no particle can get through the hole in slit.