If two light waves each of amplitude a travelling a travelling through a medium arrive at a point in opposite phase then the resultant amplitude R at that points is

Options

A. `R=0`
B. `R=a`
C. `R=2a`
D. `R=4a`

Answer

A

Explanation

`a_(1)= a_(2)= a and alpha_(1)-alpha_(2)= pi, R=?`
`R= sqrt(a_(1)^(2)+a_(2)^(2)+2a_(1) cos (alpha_(1)-alpha_(2)))`
`=sqrt(a^(2)+a^(2)+ 2 a_(1)a_(1) cos pi)`
`R =0`