Question

imagine that you are sitting in a chamber which of back to one wall and electron beam moving horizontally from back wall towards the front wall is deflected by a strong magnetic field to your right side what is the direction of magnetic field

Answer 1

Fleming's left hand rule is used to determine the direction of magnetic field. The direction of electric current will be from front wall to back wall as it is opposite to the direction of electron. Since the direction of force is towards the right side, by applying Fleming’s left hand rule, we can conclude that the magnetic field inside the chamber is in downward direction.
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Answer 2

Explanation:

The direction of the magnetic field is vertically downwards. The direction of current is from the front wall to the back wall because negatively charged electrons are moving from back wall to the front wall. The direction of magnetic force is rightward. Hence, using Fleming's left hand rule, it can be concluded that the direction of magnetic field inside the chamber is downward.