Electromagnetic waves travel in free space with the speed of___________________?
Correct answer: A. λ-rays
- A. λ-rays
- B. Positive rays
- C. Cathode rays
- D. More than sound waves
Explanation
Gamma rays, apparently intended by λ-rays, are electromagnetic waves and travel in free space at the speed of light, approximately 3.0 x 10^8 m/s. Positive rays and cathode rays are streams of particles, not electromagnetic waves. The likely wrong choice is d, because electromagnetic waves do travel faster than sound, but that option does not state the specific speed being tested.
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About Electromagnetic Waves
Electromagnetic waves consist of mutually perpendicular, oscillating electric and magnetic fields that also remain perpendicular to the direction of propagation. They travel through vacuum at the speed of light and include radio waves, microwaves, infrared, visible, ultraviolet, X-rays and gamma rays. Unlike mechanical waves, they do not require a material medium.
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