Which of the following are true?
A. Speed of light in vacuum depends on the direction of propagation.
B. Speed of light in a medium is independent of the wavelength of light.
C. Speed of light is independent of the motion of the source.
D. Speed of light in a medium is independent of intensity.
Choose the correct answer from the options given below:
A and C only
B and D only
B and C only
C and D only
Correct answer:D
Standard Method
Given: Four statements about the speed of light in vacuum and in a medium are to be checked.
Find: Which statements are true.
Analysis of Statements:
Therefore, the true statements are C and D only. The correct option is D.
Assuming that light in a medium has the same speed for all wavelengths. This is wrong because dispersion makes refractive index depend on wavelength. Check whether the question is about vacuum or a material medium before deciding.
Confusing the invariance of light speed in vacuum with properties inside a medium. The statement about source motion applies to vacuum light speed, not automatically to propagation in materials. Separate the two cases clearly.
Thinking that direction of propagation changes the speed of light in vacuum. In standard isotropic vacuum, light speed is the same in all directions. Use the postulate of special relativity for vacuum propagation.
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