The K.E. (K) of a charged particle is zero at time t, 2K at time `4t` and `4k` at time `5t` and then it remains constant upto time `8t`. Choose the correct statement/statements out of the following:

Options

A. The electric field is the only field present between t and `4t`
B. Between `5t` and `8t` only magnetic field is present
C. Both, electric and magnetic fields may be present
D. Both, electric and magnetic fields may be present between t and `4t`, but electric field is definitely present.

Answer

C, D

Explanation

(a) Since K.E. is increasing from t to `4t`, electric field is definitely present but magnetic field may also be present. Hence incorrect statement.
(b) Since K.E. is constant from `5t` to `8t_1` either only magnetic field is present or both fields are present but cancel out each other hence incorrect statement.
Thus, 'c' and 'd' are correct statments.