B. Different colors have different speeds in medium
C. Prism absorbs colors
D. Different frequencies
Answer: Option B
Solution (By JKSSB Mock Tests)
n varies with λ ⇒ v = c/n varies ⇒ different refraction angles (Snell's law). Frequency constant; wavelength changes in medium. Memory aid: 'Dispersion: n(λ) ⇒ v(λ) ⇒ different bending; violet bends most'. Optics concept frequently tested in competitive exams.
Explanation:
v = c/n = 3×10⁸/2 = 1.5×10⁸ m/s. Direct refractive index application. Memory tip: 'Higher n ⇒ slower light; v = c/n'. Optics calculation frequently tested in competitive exams.
Explanation:
Convert speeds: 18 km/h = 5 m/s, 36 km/h = 10 m/s. Using v = u + at => a = (10-5)/5 = 1 m/s². Distance s = ut + ½at² = 5×5 + ½×1×25 = 25 + 12.5 = 37.5 m. Also using average velocity: (5+10)/2 × 5 = 7.5×5 = 37.5 m. Answer A.
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