A ray of light passes from air to glass. Which quantity remains unchanged?
A. Speed
B. Amplitude
C. Frequency
D. Wavelength
Answer: Option C
Solution (By JKSSB Mock Tests)
When light crosses media, frequency remains constant as it's determined by the source. Speed and wavelength change proportionally: v = fλ, and v = c/n, so λ decreases in denser medium (glass). Amplitude may change due to reflection/transmission coefficients. Memory aid: 'Frequency is source-dependent; speed and wavelength are medium-dependent'. This fundamental wave property is frequently tested in refraction questions. Competitive exams often use this to assess understanding of wave behavior at interfaces. Always recall that color (frequency) doesn't change during refraction, though speed and wavelength do.
Explanation:
Speed constant implies magnitude of velocity constant, so kinetic energy (½mv²) is constant. Velocity changes due to direction change. Acceleration (centripetal) is directed towards centre, changes direction. Linear momentum vector changes. So only kinetic energy remains constant.
Explanation:
Pressure = Force/Area. Force = mass × acceleration, dimensions [MLT⁻²]. Area = L². So pressure = [MLT⁻²]/[L²] = [ML⁻¹T⁻²]. This is also the dimension of stress. Common exam trap: confuse with energy density which is also [ML⁻¹T⁻²].
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