The splitting of white light into seven colours is called
A. Refraction
B. Scattering
C. Dispersion
D. Total internal reflection
Answer: Option C
Solution (By JKSSB Mock Tests)
Dispersion: separation due to different refractive indices for different colours. Refraction is bending. Scattering (Tyndall effect) makes sky blue. Total internal reflection in optical fibers.
Two slabs of equal thickness and cross-sectional area have thermal conductivities K1 and K2. If they are joined in series, the equivalent thermal conductivity of the combination is:
Explanation:
For slabs in series, the rate of heat flow (H) is the same. Total resistance R_eq = R1 + R2. Since thermal resistance R = L / (KA), and total length is 2L: (2L) / (K_eq * A) = (L / K1A) + (L / K2A). Canceling L/A yields 2/K_eq = 1/K1 + 1/K2. Solving gives K_eq = 2K1K2 / (K1 + K2).
Explanation:
Power = Work/Time. Work has dimensions [ML²T⁻²], dividing by time [T] gives [ML²T⁻³]. Energy is [ML²T⁻²], force is [MLT⁻²], momentum is [MLT⁻¹]. This dimensional formula uniquely identifies power. Memory tip: Power = energy per second ⇒ dimensions include extra T⁻¹ factor. Frequently tested in dimensional analysis sections of competitive exams.
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