$\text{Coherent time} =\frac{\text{Coherence length}}{\text{Velocity of light}}=\frac{\text{L}}{\text{c}}$
Thomas Young demonstrated the phenomenon of interference in water waves.
In $1801$, he presented a famous paper to the Royal Society entitled "On the Theory of Light and Colours" which described various interference phenomena, and in $1803$ he performed his famous double$-$slit experiment.
In photometry, luminous intensity is a measure of the wavelength$-$weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The $SI$ unit of luminous intensity is the candela $(cd),$ an $SI$ base unit.
$\beta$ are stream of particles comprising of electrons moving with very high velocity, hence it cannot be polarized, while others can as they are electromagnetic waves.
Red shift happens when light from an object increases in wavelength. It occurs whenever a light source moves away from an observer.
Blue shift happens when light from an object decreases in wavelength. It occurs whenever a light source moves toward an observer.
When an object moves away from us, its light waves are stretched into lower frequencies or longer wavelengths, and we say that the light is redshifted. It also explain the expanding nature of universe.
Shifting towards red end means wavelength is increasing.
Resolving limit
$\text{d}\theta=\frac{1.22\lambda}{\text{a}}$
$=\frac{1.22\times4538\times10^{-10}}{1}$
$= 5.54 \times 10^{-7} \mathrm{rad}.$
Polarization changes when plane of vibration of polarized light changes.
Human eye is insensitive to change in polarization and hence, cannot detect polarization of light.
Newton's particle theory remained accepted for a long time when it was challenged by the double$-$slit experiment of Thomas Young $(1773-1829)$ in $1801$. This experiment clearly established that light coming from two coherent sources interferes and produces maxima and minima depending on the path difference.
The speed of light in any medium depends on the refractive index of that medium, which is an intensive property. Hence, speed of light is not affected by the elasticity and inertia of the medium.
The sum of the focal lengths of the objective and an eyepiece, in case of an astronomical telescope is equal to The length of the telescope.
Only the transverse waves can be polarized.
As the sound waves are longitudinal waves in nature whereas visible light rays and $X-$rays are transverse waves.
Thus sound waves cannot be polarized.
Interference
Christian Huygens verified the wave nature of light using interference.
When exposed to sunlight, thin films of oil on water often exhibit brilliant colors due to the phenomenon of interference.
In the case of a thin oil film, a layer of oil sits atop a layer of water. The oil may have an index of refraction near $1.5 $ and the water has an index of $1.33.$
The materials on either side of the oil film $($air and water$)$ both have refractive indices that are less than the index of the film.
Light is a form of energy that we can detect with our eyes.