Question

The velocity of a photon is:
A. Dependent on its wavelength
B. Dependent on its source
C. Equal to the cube of its amplitude
D. Independent of its wavelength

Answer 1

In quantum mechanics, it is explained that the photon exhibits wave-particle duality. This means that every quantum entity is regarded as either a particle or a wave. Therefore photons can behave either as a wave or particle.

Complete step by step answer:
A photon is defined as the smallest unit or the quantum of electromagnetic radiation. Photons are the unit of light.
Photons always move in the vacuum at a constant speed of $2.998 \times {10^8}m/s$. It is considered as the speed of light and denoted by c.
Einstein’s light quantum theory shows that the energy of a photon is the same as the oscillation frequency of Planck's constant.
Einstein concluded that the light is determined by the flow of photons and the energy of the photons is related to their height of oscillation frequency and the light intensity gives the number of photons.
When the photon is moving with velocity v, frequency $\upsilon$ and wavelength $\lambda$,
The velocity of photon is given by
$v = \lambda \upsilon$
The velocity of the photon is directly proportional to the frequency.
$v\alpha \upsilon$
When the frequency is kept constant, the velocity is directly proportional to the wavelength.
$v\alpha \lambda$
Example: For a constant frequency, when the velocity of the photon is doubled the wavelength also gets doubled.
Thus, the velocity of a photon is dependent on the wavelength.

So, the correct answer is Option A.

Note: A single photon differs from another photon by the energy it possesses. In empty space the photons travel with similar speed or velocity but the speed of the photon slows down when they pass to different media like water or glass.