A positively-charged particle (alpha-particle) projected towards the west is deflected towards the north by a magnetic field. The direction of the magnetic field in which direction?
A. towards south
B. towards east
C. downward
D. upward

Hint: Since the positively charged molecule is anticipated towards west, so the heading of current is towards west. Presently the redirection is towards north, so the force is towards north.

Complete step-by-step answer:
The correct answer is D.
As indicated by Fleming's Left Hand Rule, if the focus finger focuses toward current (west), thumb focuses toward force (north), at that point the forefinger focuses toward the attractive field (upwards).
In this manner, the attractive field is in an upward direction. Alpha particles are positively charged, beta particles are contrarily charged, and gamma radiation is electrically impartial.
This implies the alpha and beta radiation can be avoided by electric fields, yet gamma radiation can't recollect that contrary charges act downward.
Beta particles are adversely charged so they will be pulled in towards a positively charged plate. What's more, positive alpha particles will be pulled in towards an adversely charged plate. Because they comprise of charged particles, alpha and beta radiation can likewise be redirected by attractive fields. Similarly likewise with electric fields, gamma radiation isn't avoided by attractive fields.
At the point when alpha and beta particles move in attractive fields they experience an avoiding force - given their motion doesn't resemble the field.

Note: Alpha particles, similar to helium cores, have a net turn of zero. Because of the instrument of their creation in standard alpha radioactive decay, alpha particles by and large have a kinetic energy of around 5 MeV, and a velocity in the region of 5% the speed of light.
They are an exceptionally ionizing type of molecule radiation, and (while coming about because of radioactive alpha decay) have low infiltration depth. They can be halted by a couple of centimeters of air, or by the skin.