Question

Which of the following are true?
A. Speed of light in vacuum is dependent on the direction of propagation. 
B. Speed of light in a medium is independent of the wavelength of light. 
C. The speed of light is independent of the motion of the source. 
D. The speed of light in a medium is independent of intensity.
Choose the correct answer from the options given below:

• A. C and D only
• B. B and D only
• C. B and C only
• D. A and C only

Hint:

For questions on the speed of light:
• In vacuum, light speed is constant and independent of source motion.
• In a medium, dispersion occurs, making speed wavelength-dependent.

Answer 1

The Correct Option is A

To solve the problem, let's evaluate each statement for their validity:

1. A. Speed of light in vacuum is dependent on the direction of propagation.
   This statement is false. The speed of light in a vacuum is a constant, approximately 299,792,458 \, \text{m/s}, and is isotropic, meaning it is independent of the direction of propagation.
2. B. Speed of light in a medium is independent of the wavelength of light.
   This statement is false. The speed of light in a medium actually depends on the wavelength due to the phenomenon of dispersion, where different wavelengths of light travel at different speeds resulting in separation of colors, like in a prism.
3. C. The speed of light is independent of the motion of the source.
   This statement is true. According to the principle of the constancy of the speed of light in Einstein's theory of relativity, the speed of light in a vacuum is constant and does not depend on the motion of the light source.
4. D. The speed of light in a medium is independent of intensity.
   This statement is true. The speed of light in a medium is determined by the medium’s refractive index and is generally unaffected by the light's intensity.

Based on these evaluations, the correct answer is C and D only, as statements C and D are true.