Assertion: If the accelerating potential of an electron is doubled then its velocity becomes `1:4` times.
Reason: If the move on a circular path will same velcoity.

Options

A. If both assertion and reason are true and reson is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If assertion and reason both are false.

Answer

C

Explanation

If `V` is the accelerating potential and `v` is the velocity of electron, then
`eV = (1)/(2)mv_(2)`
or `V prop sqrt(V)`
`:. (V_(1))/(V_(2)) = sqrt((V_(1))/(V_(2)))`
Here, `V_(1) = V, V_(2) = 2V, v_(1)v_(2) = ?`
`:. (v)/(v_(2)) = sqrt((V)/(2V)) =(1)/(sqrt(2))`
`rArr v_(2) = sqrt(2v) = 1.4 v`
Reason is a false statement, as conditions must be discussed for electron to move on circular path.