Concept: Cathode rays are streams of highly energetic electrons. Because electrons possess rest mass, they are bound by the laws of relativity.
Formula: None required.
Solution: - Cathode rays are electrons. Electrons are material particles with a definitive mass (\( 9.1 \times 10^{-31} \text{ kg} \)).
- According to Einstein's theory of relativity, no object with mass can ever reach or exceed the speed of light (\( c \)) in a vacuum.
- While cathode rays travel extremely fast (often close to light speed depending on the accelerating voltage), they can never travel exactly at the velocity of light.
- Therefore, the statement that they travel with the velocity of light is false.
Why other options are incorrect: Options A, B, and C (a duplicate) are true statements. Electrons are material particles with mass and they travel with a measurable, definite velocity in the tube.
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