By which one of the following, an old written material which cannot be read easily, can be read ?

Old written materials, such as manuscripts that have become faded, charred, or obscured over time, can be read using Infrared (IR) rays. Infrared imaging and photography have been used since the 1920s to assist in reading manuscripts by enhancing the contrast between the ink and the background material [t3]. While ultraviolet (UV) light is also commonly used for fluorescence imaging of palimpsests [t1][t8], infrared spectrum imaging is a standard non-destructive technique for recovering text from cultural heritage objects that are otherwise illegible [t4]. IR rays are particularly effective because many inks absorb or reflect infrared light differently than the underlying parchment or paper, allowing hidden or faded text to become visible to specialized sensors [t8]. Although X-ray fluorescence (XRF) is used for high-value obscured texts [t6], IR-rays remain a primary and more accessible method for general manuscript recovery and legibility enhancement [t3][t4].