How many Times greater is the speed of infrared light (=800 nm) than the speed of violet light (=400 nm) in a vaccum?
The correct answer and explanation is:
The speed of light in a vacuum is constant for all types of light, regardless of its wavelength. This is because in a vacuum, the speed of light (denoted as “c”) is approximately 299,792,458 meters per second, and this value is the same for all electromagnetic waves, including infrared, violet light, and others.
However, the key difference between infrared light (wavelength = 800 nm) and violet light (wavelength = 400 nm) lies in their frequency and energy, not their speed. The wavelength and frequency of light are inversely related through the equation: c=λ×νc = \lambda \times \nu
Where:
- cc is the speed of light (in vacuum),
- λ\lambda is the wavelength of the light,
- ν\nu is the frequency of the light.
Since the speed of light is constant, the frequency of light changes in inverse proportion to its wavelength. For shorter wavelengths (like violet light), the frequency is higher, and for longer wavelengths (like infrared light), the frequency is lower.
To compare the two light types, consider the relationship of wavelength and frequency:
- Infrared light has a longer wavelength (800 nm), meaning it has a lower frequency compared to violet light.
- Violet light has a shorter wavelength (400 nm), meaning it has a higher frequency.
Since the speed of light is constant in a vacuum, the speed of infrared light is equal to the speed of violet light. Therefore, infrared light is not “faster” than violet light in a vacuum.
In summary, the speed of infrared light is not greater than that of violet light. Both travel at the same speed in a vacuum: approximately 299,792,458 meters per second. The differences between them lie in their wavelength and frequency, not in speed.