Real image (such as the images on the right), real rays of light are always represented by full, solid lines; perceived or extrapolated rays of light are represented by dashed lines. A real image occurs where rays converge, whereas a virtual image occurs where rays only "appear" to converge. Real images can be produced by concave mirrors and converging lenses, only if the object is placed further away from the mirror/lens than the focal point and this real image is inverted. As the object approaches the focal point the image approaches infinity, and when the object passes the focal point the image
Grenz rays palmoplantar pustulosis, neurodermatitis, pruritus ani and pruritus vulvae. They have been reported to be helpful for lichen planus, Grover's disease, Darier's disease, Hailey–Hailey disease and histiocytosis X. Grenz rays have also been used for treatment of actinic keratosis and Bowen's disease. Grenz rays Grenz rays are part of the electromagnetic spectrum comprising low energy (ultrasoft) X-rays. These were first investigated by Gustav Bucky in 1923 using a cathode vacuum tube with a lithium borate glass window, which he labeled Grenz rays as he believed that the biological effects resembled those of UV light and traditional X-rays and hence were on