Assertion (A),If electrons travel undefeccted by the electric field` E` and magnetic field B then the velocity of electrons is given by `V=e/b`.
Reason `(R )`: When both electric and magnetic field are applied simultaneously on electron beam. If force due to electric field is equal and opposite to force due to magnetic field then they travel undeflected.

Options

A. `A` and `R` are true and `R` is the correct explaination of `A`
B. `A` and `R` are true and `R`is not the correct explaination of `A`
C. `A` is true and `R` is false.
D. `A` is false but `R` is true

Answer

A