Key relation for light

For any electromagnetic wave, $c = \nu \lambda$ where:

• $c$ = speed of light in vacuum,
• $\nu$ = frequency,
• $\lambda$ = wavelength.

Compare red and blue light

In the visible spectrum:

• Red light has a longer wavelength.
• Blue light has a shorter wavelength.

Since $c$ is constant in vacuum, $\nu = \frac{c}{\lambda}$ So if wavelength changes, frequency must also change.

Therefore:

• Red and blue light have different wavelengths.
• Red and blue light also have different frequencies.

Check each option

• A: Different frequencies and same wavelengths → Incorrect, because their wavelengths are not the same.
• B: Different frequencies and different wavelengths → Correct.
• C: Same frequencies and different wavelengths → Incorrect, because different wavelengths imply different frequencies.
• D: Same frequencies and same wavelengths → Incorrect.

Final answer

The correct option is: $\boxed{\text{B}}$