A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field
(a) towards south
(b) towards east
(c) downward
(d) upward
By Fleming's Left-hand rule,
Keeping the thumb, forefinger and middle finger in the mutually perpendicular directions. The middle finger represents the direction of the current (in the direction of motion of positive charge: towards the West), the thumb represents the force (towards the North), then the forefinger represents the direction of the field (upward)
The direction of the Magnetic field will be upward.
Hence, Option (d) is the correct option.