(a) Name the electromagnetic radiation used to detect fake currency.
(b) Redraw the diagram given below and complete the path of the light ray AB through the glass prism till it emerges out of the prism. Critical angle of the glass is 42\(^\circ\).
Show Hint
When a ray hits a boundary, always find the angle of incidence and compare it to the critical angle. If \(i>c\), TIR occurs. If \(i<c\), refraction occurs. If \(i = c\), the ray grazes the surface.
Step 1: Understanding the Concept:
Specific electromagnetic radiations can cause certain substances to fluoresce (glow), which is used for security identification. Step 2: Detailed Explanation:
Genuine currency notes have certain marks or patterns printed with special fluorescent ink.
These marks are invisible under ordinary visible light but become visible and glow when exposed to Ultraviolet (UV) radiations.
Fake currency usually lacks these sophisticated fluorescent security features. Step 3: Final Answer:
Ultraviolet radiations are used to detect fake currency.
