b
\(\Rightarrow E =\overrightarrow{ E }=30 \hat{ j } \sin \left(1.5 \times 10^{7} t -5 \times 10^{-2} x \right) V / m\)

\(\Rightarrow B \Rightarrow E / V \Rightarrow \frac{30}{1.5 \times 10^{7}} \times 5 \times 10^{-2}\)

\(\Rightarrow 10^{-7}\) Tesla

\(\Rightarrow F _{ mag }= q (\overrightarrow{ V } \times \overrightarrow{ B })=| q VB |\)

\(=1.6 \times 10^{-19} \times 0.1 \times 3 \times 10^{8} \times 10^{-7}\)

\(=4.8 \times 10^{-19} N\)