Final answer:
When the wavelength of a photon is increased by a factor of two, its frequency decreases by the same factor.
Step-by-step explanation:
When the wavelength of a photon is increased by a factor of two, its frequency decreases by the same factor. This is because there is an inverse relationship between wavelength and frequency in electromagnetic waves.
As the wavelength increases, the frequency decreases and vice versa. This can be represented by the equation:
Speed of light = Wavelength × Frequency
If the wavelength doubles, the frequency will be halved, resulting in a decrease in frequency.