Question

The colour of light is determined by its
A. Wavelength
B. Phase
C. Velocity
D. Amplitude

Answer 1

Hint: The energy of the electromagnetic radiation is used to characterize light and is directly proportional to its frequency and inversely proportional to the wavelength. The wavelengths in VIBGYOR are characterized on the basis of either their frequency or wavelength.

Detailed step by step solution:
The light rays are electromagnetic waves in nature which are actually transverse waves that have crests and troughs. The wavelength of light can be defined as the distance between two crests or two troughs. It can also be defined as the distance travelled by the wave to complete one time period.

The frequency of light is inversely proportional to the wavelength of the light and is equal to the reciprocal of time period of the wave.
$c = \lambda \nu $
The colour of light is defined on the basis of either its wavelength or its frequency. Hence, the correct answer is option A.
Additional information:
The wavelengths of various radiation in VIBGYOR or visible radiation are given as follows:
Violet: 400 nm
Indigo: 440 nm
Blue: 460 nm
Green: 500 nm
Yellow: 570 nm
Orange: 590 nm
Red: 620 nm

Note: 1. The phase of a wave can be understood by the fact that wavelength of a wave can be defined in terms of phase such that it is equal to distance between two points that are in phase with each other.
2. The velocity of light wave is constant for all frequencies and wavelengths and is given as
$c = 3 \times {10^8}m/s$
3. The amplitude of a wave can be defined as the maximum displacement of a wave from its mean position.