Answer : The frequency decreases by a factor of 2.
Explanation :
Given that the wave travels at a constant speed. The speed of the wave is given as :
Where
υ is the frequency of the wave
and λ is the wavelength of the wave.
In this case, the speed is constant. So, the relation between the frequency and the wavelength is inverse.
If the wavelength increases by a factor of 2, its frequency will decrease by a factor of 2.
Hence, the correct option is (A) " The frequency decreases by a factor of 2 ".