Question

The speed of electromagnetic waves is the same

• A. for all wavelengths
• B. in all media
• C. for all intensities
• D. for all frequencies

Answer 1

The correct option is C

for all intensities

The explanation for the correct option:

Correct option: (C)

1. The speed of light or an electromagnetic wave depends upon the medium through which it travels,$$v={\displaystyle \frac{c}{n}}$$
2. Here, $n$ is the refractive index of the material or the medium,$v$ is the velocity of the electromagnetic wave traveling in the medium, and $c$ is the speed of light in a vacuum.
3. So from the formula, we can see the speed of the electromagnetic wave is independent of the intensity of the electromagnetic wave.
4. So, the speed of Electromagnetic waves is the same for all intensities of Electromagnetic waves.
5. Therefore, this option is correct.

Explanations for incorrect options:

Incorrect Option (A):

1. The speed of Electromagnetic waves is the product of wavelength and the frequency of the EMW.
2. $$c=f\lambda$$, Here, $c$ is the speed of light in a vacuum; $f$ is the frequency of the light, and $$\lambda$$is the wavelength of the light.
3. The speed of EMW changes for different wavelengths.
4. Therefore, this option is incorrect.

Incorrect Option (B):

1. The speed of Electromagnetic waves reduces when passing through denser media.
2. So, the speed of Electromagnetic waves changes for different media.
3. Therefore, this option is incorrect.

Incorrect Option (D):

1. The speed of Electromagnetic waves is the product of wavelength and the frequency of the EMW.
2. $$c=f\lambda$$, Here, $f$ is the frequency of the light, $c$ is the speed of light in a vacuum, and $$\lambda$$is the wavelength of the light.
3. The speed of Electromagnetic waves changes for different frequencies.
4. The speed of light or an electromagnetic wave depends upon the frequency and is independent of the intensity.
5. Therefore, this option is incorrect.

Hence option C is the correct answer.