# Deflection distance for an electron beam in an electric field

• Bolter
Bolter
Homework Statement
See question below
Relevant Equations
F = qE
Have tried doing this question but I'm a bit confused on where I'm going wrong

This is what I have done but get a value that doesn't match to any of the options given above?

Any help would be really appreciated, Thanks!

Homework Helper
Gold Member
I agree with your answer of 17.6 cm. Your work looks very good. But in your diagram, if the electric field is downward, would the electron be deflected downward?

Bolter
I agree with your answer of 17.6 cm. Your work looks very good. But in your diagram, if the electric field is downward, would the electron be deflected downward?

Sorry my field line directions should be reversed (going from positive to negative)

So the question must have a mistake then I guess. I believe the first option would’ve been the right answer but maybe the person who wrote this misplaced the decimal point position and instead got 1.76cm and not 17.6cm

Mentor
Sorry my field line directions should be reversed (going from positive to negative)

So the question must have a mistake then I guess. I believe the first option would’ve been the right answer but maybe the person who wrote this misplaced the decimal point position and instead got 1.76cm and not 17.6cm
Yup. Given the question-given values the beam will impact the positive plate about halfway through the parallel plate channel. So original problem statement FAIL. This happens frustratingly frequently, especially when older problem sets are "updated" to change the working values to "refresh" the problem for new editions of texts or exams.

Bolter and TSny