Which one of the following statements is *not* correct for light rays ?
Light travels at different speeds in different media.
Light travels at almost 300 million metres per second in air.
Light speeds down as it leaves a water surface and enters the air.
Light speeds up as it leaves a glass surface and enters the air.
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-1 – 2021
– Light travels fastest in a vacuum (approximately 3 x 10⁸ m/s).
– The speed of light is slower in optically denser media (like water or glass) than in optically less dense media (like air or vacuum).
– B) is correct: The speed of light in air is very close to its speed in vacuum.
– C) is incorrect: Water is optically denser than air. When light moves from a denser medium (water) to a less dense medium (air), its speed *increases*.
– D) is correct: Glass is optically denser than air. When light moves from a denser medium (glass) to a less dense medium (air), its speed *increases*.