Question

A source of light lies on the angle bisector of two plane mirrors inclined at angle `theta`. The value of `theta`, so that the light reflected from one mirror does not reach the other mirror will be.
A. `theta ge 120^(@)`
B. `theta ge 90^(@)`
C. `theta le 120^(@)`
D. `theta lt 30^(@)`

Answer 1

(a) `n=360/(theta)`
Number of images `N=n,` which is odd `=n-1`
For the given condition,successive reflection takes place. So the number of images will be `Nle2`.
`n-1le2`
`nle3`
`360/(theta)le3`
`120le thetaimpliestheta ge 120^(@)`