CBSE Class 10 Answered

Hi dear,

The point here is that the reflected ray is always rotated from the incident ray by twice the angle of incidence. If the incident ray doesn't move and a mirror rotation of theta changes the angle of incidence by theta, then the reflected ray rotates by 2*theta. Imagine the 45 degree angle of incidence case. Your flashlight beam is reflected 90 deg to one side. Now rotate the mirror 90 deg so it's 45 deg in the other direction. The beam is reflected 90 deg to the other side, rotated by 180 deg.

Hope this helps.

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