A ray of light travels from glass (μ=1.5) to air. Critical angle is
A. sin⁻¹(1/3)
B. sin⁻¹(1.5)
C. sin⁻¹(2/3)
D. sin⁻¹(1/1.5)
Answer: Option D
Solution (By JKSSB Mock Tests)
sin C = 1/μ = 2/3 ≈ 0.6667, C = sin⁻¹(2/3). So option A: sin⁻¹(2/3). Wait sin C = n2/n1 = 1/1.5 = 2/3. So C = sin⁻¹(2/3). Option A is sin⁻¹(2/3). I'll correct to A.
Explanation:
T = 2π√(m/k): depends on mass and spring constant only, not gravity. Weightlessness doesn't affect spring force. Memory aid: 'Spring period: independent of g; pendulum period: depends on g'. Oscillations concept frequently tested in competitive exams.
Explanation:
Radiation transfers heat via electromagnetic waves and requires no medium, thus works in vacuum (e.g., solar energy reaching Earth). Conduction needs direct contact between particles; convection requires fluid movement. Vacuum lacks matter for conduction/convection. Memory tip: 'Radiation = only mode in vacuum'. This fundamental distinction is frequently tested in competitive exams. Applications include thermos flasks (minimizing all three modes) and space technology. Always recall that radiation speed is light speed, while conduction/convection are much slower.
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