A forensic scientist wants to reveal hidden writings or alterations in a document. Which technique should he use?

chromatography

chemical tests

handwriting analysis

ultraviolet or infrared imaging

ultraviolet or infrared imaging - when you hold a paper up to light it may reveal somthing that was'ent there if you wrote it in lemon juice. In a similar way, forsencic scientists use UV lights to reveal any alteration or hidden writings on a piece of paper.

Answer: ultraviolet or infrared imaging

Explanation:

The forensic document examination involves the decipherment of secret writings written on the document also some of the alteration in the original document done by using invisible chemical solutions. These writings and alterations can be revealed by the ultraviolet or infrared imaging techniques. The material used in the ink of secret writing and the chemical solution can absorb the radiations from UV and infrared rays which emits their own light with particular wavelength along with the writing part which can be detected by using suitable devices.