The phenomenon of total internal reflection requires the light to travel from:
A. Any medium to vacuum
B. Glass to air
C. Air to glass
D. Water to glass
Answer: Option B
Solution (By JKSSB Mock Tests)
Total internal reflection (TIR) occurs only when light travels from denser medium to rarer medium (e.g., glass to air, water to air) and angle of incidence exceeds critical angle. Air to glass (A) causes refraction toward normal; water to glass (C) may or may not cause TIR depending on refractive indices; vacuum is rarer than any medium but TIR requires denser→rarer. Memory aid: 'TIR condition: denser→rarer AND i > θ_c'. This optics condition question is frequently tested in competitive exams. Always verify both conditions (medium order and angle) for TIR; competitive exams often test common misconceptions about direction of travel.
Explanation:
Elastic collisions conserve both total momentum and total kinetic energy. Inelastic collisions conserve only momentum. This distinction is fundamental in collision analysis. Memory aid: 'Elastic = KE + momentum conserved; Inelastic = momentum only'. Frequently tested concept to differentiate collision types in competitive exam mechanics sections.
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