Iska option iska nicha wala hai
Dear student,
As there are no objects seen in the image and the rays seem parallel to each other, it can be inferred that the rays are coming from infinity. Rays that come from infinity will converge or appear to converge to a point when it passes an optical device like a lens or a mirror, the converging point being it’s focal length. In the given figure, the rays come from infinity, pass the optical device, and converge to a point on the screen at a distance 20cm from it. This means that it is a lens (as rays pass through the optical device to form real images) with focal length20cm. As the image is formed on the other side of the lens, and as the image is real (concave lens always forms virtual image), the lens is a converging lens or convex lens.
Now coming to the optical device- Y, the rays are reflected from Y which means that it is a mirror. The rays are coming from infinity in this case as well and they converge to a point on the screen at a distance 25cm from the mirror. So the focal length of the mirror is 25cm. But in this case, the focal point is formed on the same side of the mirror as that of the emerging rays, and a real image is formed. This means that Y is a concave mirror as only concave mirrors are capable of forming real images.
Option c is correct
Regards
As there are no objects seen in the image and the rays seem parallel to each other, it can be inferred that the rays are coming from infinity. Rays that come from infinity will converge or appear to converge to a point when it passes an optical device like a lens or a mirror, the converging point being it’s focal length. In the given figure, the rays come from infinity, pass the optical device, and converge to a point on the screen at a distance 20cm from it. This means that it is a lens (as rays pass through the optical device to form real images) with focal length20cm. As the image is formed on the other side of the lens, and as the image is real (concave lens always forms virtual image), the lens is a converging lens or convex lens.
Now coming to the optical device- Y, the rays are reflected from Y which means that it is a mirror. The rays are coming from infinity in this case as well and they converge to a point on the screen at a distance 25cm from the mirror. So the focal length of the mirror is 25cm. But in this case, the focal point is formed on the same side of the mirror as that of the emerging rays, and a real image is formed. This means that Y is a concave mirror as only concave mirrors are capable of forming real images.
Option c is correct
Regards