Final answer:
The angles the velocity of the electron makes with the magnetic field are 30° and 60°, so the correct option is B.
Step-by-step explanation:
To find the angle that the velocity of the electron makes with the magnetic field, we can use the formula for the magnetic force on a moving charge, which is F = qvBsin(θ), where F is the magnetic force, q is the charge of the electron, v is the velocity of the electron, B is the magnetic field strength, and θ is the angle between the velocity and the magnetic field. We are given F as 1.40×10-16 N, the speed v as 4.00×103 m/s, the magnetic field B as 1.25 T, and the charge of the electron q as -1.60×10-19 C.
The negative sign for the charge of the electron does not affect the calculation of force magnitude but indicates the direction of the force. From the provided formula, rearranging for sin(θ), we get sin(θ) = F / (qvB). Plugging the values into this equation: sin(θ) = (1.40×10-16 N) / ((1.60×10-19 C)(4.00×103 m/s)(1.25 T)), solving this gives us sin(θ) ≈ 0.875. This means that θ ≈ 30° or θ ≈ 150°, but since magnetic force is always perpendicular to both the velocity and the magnetic field, the relevant angles are 90° - 30° = 60° and 180° - 150° = 30°. Therefore the angles 30° and 60° are the two solutions to the question. Hence, we choose any one option and mention the correct option in the final answer: Option B.