1. Assertion (A): Small glass beads fixed on traffic signals glow brightly when light falls upon them. 2. Reason (R): Light is totally reflected when the angle of incidence exceeds a certain critical value and light travelling in a denser medium is reflected from a rarer medium.

1. Assertion (A): Small glass beads fixed on traffic signals or road signs do glow brightly when light falls upon them. This is due to retroreflection, where light is reflected back towards its source with minimum scattering. This makes the signals highly visible to drivers at night when illuminated by headlights. So, Assertion (A) is true. 2. Reason (R): The statement describes the phenomenon of total internal reflection (TIR), which occurs when light travels from a denser medium to a rarer medium at an angle of incidence greater than the critical value. While TIR is a real phenomenon and the description is correct, the glowing of glass beads is primarily due to refraction and reflection (often specifically retroreflection, which can involve TIR within the bead's structure or shape). However, the Reason (R) itself, explaining TIR, is a correct statement of physics. 3. Explanation Check: Does the principle of Total Internal Reflection (light going from denser to rarer medium) explain why beads glow when light *falls upon them* (light going from rarer air to denser glass)? While TIR might occur *inside* the bead to redirect light back, the reason as stated (denser to rarer for reflection) is the condition for TIR itself, not the direct explanation for the initial glowing upon illumination. The shape and refractive properties causing light to be focused and reflected back towards the source (retroreflection) is the more complete explanation. Therefore, R does not fully and correctly explain A, although it describes a related optical principle. 4. Conclusion: Both A and R are true statements, but R is not the correct and complete explanation for A.