Taking into account the definition of wavelength, frecuency and propagation speed, the wavelength of a wave with a frequency of 2.45×10⁹ Hz is 1.22×10⁻¹ m (second option)
Wavelength is the minimum distance between two successive points on the wave that are in the same state of vibration. It is expressed in units of length (m).
Frequency is the number of vibrations that occur in a unit of time. Its unit is s⁻¹ or hertz (Hz).
The propagation speed is the speed with which the wave propagates in the medium, that is, it is the magnitude that measures the speed at which the wave disturbance propagates along its displacement.
The propagation speed relate the wavelength (λ) and the frequency (f) inversely proportional using the following equation:
v = f× λ
All electromagnetic waves propagate in a vacuum at a constant speed of 3×10⁸ m/s, the speed of light.
Therefore, the previous expression establishes an inversely proportional relationship between the frequency and the wavelength: The higher the frequency, the lower the wavelength and when the frequency is lower, the greater the wavelength.
In this case, you know:
- v=3×10⁸ m/s
- f=2.45×10⁹ Hz
- λ= ?
Replacing:
3×10⁸ m/s= 2.45×10⁹ Hz× λ
Solving:
λ= 3×10⁸ m/s ÷ 2.45×10⁹ Hz
λ= 1.22×10⁻¹ m
In summary, the wavelength of a wave with a frequency of 2.45×10⁹ Hz is 1.22×10⁻¹ m (second option)