Optics 1
Classical Mechanics
Level
2
Ray I comes to optical system as shown in the figure given below. Ray reflects from the mirror placed inside the sphere in 1 direction. How much we must rotate mirror to make reflected ray follows path 2.
The answer is 22.5.
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1 solution
As the mirror is turned through A degrees, the reflected ray turns through 2A degrees. We desire to turn the ray 1 through 45 degrees hence mirror must be turned through 45/2 = 22.5 degrees........................
The reason : When the incident ray is turned, reflected ray turn in opposite direction by same angle. But here incident ray is fixed, hence the mirror turns and the reflected ray also turns again, that is its total turn is twice.