When a wave travels from one medium to another, which of its properties never changes?
A. Wavelength
B. Amplitude
C. Frequency
D. Velocity
Answer: Option C
Solution (By JKSSB Mock Tests)
When a wave (like light or sound) changes mediums, its velocity changes due to the new medium's optical or mechanical density. Wavelength changes proportionally with velocity (v = fλ). However, frequency is determined solely by the source generating the wave and the energy of the photons/particles, and it remains absolutely constant.
Assertion (A): Light year and astronomical unit both represent dimensions of length. Reason (R): Light year is the time taken by light to travel from the Sun to the Earth.
A.A is true but R is false.
B.Both A and R are true and R is the correct explanation of A.
C.Both A and R are true but R is NOT the correct explanation of A.
Explanation:
Assertion (A) is true because both light year and astronomical unit (AU) are units used to measure massive astronomical distances (lengths). Reason (R) is false because a light year is the distance light travels in a vacuum in one Earth year, not the time taken to travel from the Sun to Earth (which is about 8.3 minutes).
Explanation:
Newton's law of gravitation: F ∝ 1/r². If distance r becomes r/2, new force F' ∝ 1/(r/2)² = 4/r² = 4F. So force quadruples. This inverse square law is fundamental for gravitational, electric, magnetic forces.
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