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Uniform magnetic fields of different strengths (B 1 and B 2 ), both normal to the plane of the paper exist as shown in the figure. A charged particle of mass m and charge q, at the interface at an instant, moves into the region 2 with velocity v and returns to the interface. It continues to move into region 1 and finally reaches the interface. What is the displacement of the particle during this movement along the interface?

1. ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − 2 1 1 B B 1 qB mv
2. ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − 1 2 1 B B 1 qB mv
3. 2 B B 1 qB mv 1 2 1 × ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −
4. ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − 2 1 1 B B 1 qB mv × 2

Correct answer: ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − 2 1 1 B B 1 qB mv × 2

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