1. Vanishing Body

Inside the window are two vertical plane mirrors connected at an angle of 103 degrees. According to the formula of multiple reflections, the number of images formed would be 2.5. Two of the images are formed at the left and right mirror surfaces respectively, while the remaining 0.5 image is formed at the intersection in the middle. Since you are standing far away from the mirrors, your scope of vision is limited to that 0.5 image at the intersection. The missing portion is your vanished head and body.

2. Twins

Inside the window are two vertical plane mirrors connected at an angle of 78 degrees. According to the formula of multiple reflections, the number of images formed would be 3.6. Two of the images are formed at the left and right mirror surfaces respectively, while the remaining 1.6 image is formed at the intersection in the middle. Since you are standing far away from the mirrors, your scope of vision is limited to that 1.6 image at the intersection. The excess portion is the extra head and body.

3. Semi-transparent Mirror

The reflectivity of a semi-transparent mirror is lower than that of a normal plane mirror. When light shines on a semi-transparent mirror, only a portion of the light is reflected and the rest will pass through. If the light intensity is not balanced on both sides of the mirror, the brighter image will eclipse the dimmer one. Therefore, people at the dimmer side will see the object at the brighter side, while people at the brighter side will only see their own reflections.