Will Julian still be able to see the test card?Explain. Thanks
The answer is NO, he will not be able to see the card after the upper half of the mirror is covered (see the figure below). The image of the card in the plane mirror is formed at an equal distance d behind the mirror, the line from the card to its image being perpendicular to the mirror plane (symmetry of the image to the object with respect to plane mirror). The line of sight drawn from Julian eye to the card image intersects the curtain that covers the upper half of the mirror, so that the card image will be not visible to him.