An electron is projected as shown with speed `u`. If electron just fails to strike the upper plate, find range. (distance from starting point at which electron strike the lower plate again). Consider only electric force.

Answer

8

Explanation

`ucosthetaxxt=R` .(1)
`darra=((qE)/(m))`
`((u)/(sqrt(2)))=((qE)/(m))(t)/(2)impliest=(2mu)/(sqrt(2)qE)` .(2)
`((u)/(sqrt(2)))^(2)=2((qE)/(m))dimplies(qE)/(m^(2))=(u^(2))/(4d)` ..(3)
`impliest=(2u)/(sqrt(2)u^(2))(4d)=(4sqrt(2)d)/(u)`
put in (1)
`R=((u)/(sqrt(2)))((4sqrt(2)d)/(u))=4d`