Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror \left(\mathrm{M}_{1}\right)(M
1
) and parallel to the second mirror \left(\mathrm{M}_{2}\right)(M
2
) is finally reflected from the second mirror \left(\mathrm{M}_{2}\right)(M
2
) parallel to the first mirror \left(\mathrm{M}_{1}\right) .(M
1
). The angle between the two mirrors will
