Optics

Images formed by Two Plane Mirrors

The number of images formed by two plane mirrors forming an angle depends on the angle between them and whether the object is placed symmetrically between the mirrors. The image formed by one mirror acts as the object for the other, as long as the image lies in the object half of the plane for the other mirror. If the object is at the back of the mirror, no light from the object can fall on the mirror. All the images will be of the same intensity of the mirrors are infinite (semi-infinite), so that the amount of light that is seen to form an image is the same for all images. However, for finite mirrors, the amount of light is substantially lower for the images after the first couple of images, so that they would be fainter. The above statements assume that there is no loss in reflection.

Mirrors and Image forming space

If an object is placed between three mutually perpendicular mirrors, there are 7 images produced. Let the co-ordinates of the point be (a, b, c). The total images formed due to the mirrors in the xy, yz, and zx planes are all the different combinations of a, -a, for the first, b, -b for the second, and c, -c for the third respectively. This gives rise to 2 x 2 x 2 = 8 possibilities, where one of them coincides with the object (a, b, c).

Images by Perpendicular Mirrors

The intensity of Light

VCD in Linux

The automatic mounting process in Mandriva fails for a vcd. Attempts to mount will mount the first track, which is about 2 MB, and gives a bunch of errors in dmesg. However, the installed k3b program handles it well, with some quirks.

The Windows™ operating system is able to read files off the vcd, and you can copy the dat file from it. This file can be played in Linux using xine or kmplayer. However, k3b cannot make a vcd out of it–it demands an mpeg file. You can try and use some utilities to convert this dat file to an mpeg, but that is probably too much bother.

In k3b, there is a copy cd option, but that cannot copy a vcd as it has more than one track. You will need to rip the vcd onto your hard drive. k3b uses the vcdxrip program to do this and this will create an mpeg on the hard drive. This can also be played in all the standard media players in Linux. This file can be burned with k3b using the create vcd command. The vcd so created works well in standalone vcd players.