Optics: constraints and other objects

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The principal rays emanating from an object are drawn. You can click-drag the tip of the arrow-shaped object inside the pink box (the position is given in centimeters and the angle is given in degrees). A red curtain covers part of the animation and therefore you cannot see the rays in that region.  What kind of mirror is covered by the curtain?  Start

Interactive Hint

Remove the curtain to see the rays. Remove curtain