Question

Which of the following properties of light conclusively support the wave theory of light?
$(A)$ Light obeys the law of reflection.
$(B)$ The speed of light in water is smaller than the speed in the vacuum.
$(C)$ Light doesn’t show interference.
$(D)$ Light shows a photoelectric effect.

Answer 1

Hint : Fundamental constants are commonly thought to have the same value across spacetime, implying that they are independent of location and time. However, several ideas have proposed that the speed of light may have varied through time. Although no solid evidence for such modifications has been discovered, study into them is still ongoing.

Complete step-by-step solution:
The photoelectric effect demonstrates light's particle nature. The particle nature of light cannot explain why light travels slower in water than it does in a vacuum. However, the wave theory of light can explain it.
 In a vacuum with a refractive index of $$1.0$$, light travels at over $$300,000$$kilometers per second, but it slows down to $$225,000$$ kilometers per second in water (refractive index of $$1.3$$) and $$200,000$$kilometers per second in glass (refractive index of $$1.5$$).
When the light enters a medium with a high refractive index, the light slows down, the wavelength shortens, and the light bends toward the normal line. If the light enters a medium with a low refractive index, the light speeds up, the wavelength lengthens, and the light bends away from the normal line.
As a result, option (b) is correct.

Note:The speed at which light waves propagate in a vacuum is independent of both the wave source's motion and the observer's inertial frame of reference. After being influenced by Maxwell's theory of electromagnetism and the absence of evidence for the luminiferous aether, Einstein proposed this invariance of the speed of light in $$1905$$; it has since been repeatedly validated by various experiments.