(i) The red colour has longer wavelength.
(ii) So, it can travel for longer distance and will be seen clearly. So red colour is used in traffic signals.

(i) When sunlight passes through the atmosphere the blue colour (shorter wavelength) is scattered to a greater extent than the red colour (longer wavelength).
(ii) This scattering causes the sky to appear in blue colour.

(i) The focal length of eye lens is reduced or the distance between eye lens and retina increases.
(ii) Hence the far point will not be infinity for such eyes and the far point has come closer, with this defect, nearby object can be seen clearly but distant objects cannot be seen clearly.

The ability of the eye lens to focus nearby as well as the distant objects is called power of accommodation of the eye.

Rayleigh's scattering law states that "The amount of scattering of light is inversely proportional to the fourth power of its wavelength.
Amount of scattering \(\text { 's' } \propto \frac{1}{\lambda^{4}}\)

When a beam of white light or composite light is refracted through any transparent media such as glass or water, it is split into its component colours. This phenomenon is called as dispersion of light.

Snell's law state that, the ratio of the sine of the angle of incidence and sine of the angle of refraction is equal to the ratio of refractive indices of the two media.
\(\frac{\sin i}{\sin r}=\frac{\mu_2}{\mu_1}\)

The ratio of speed of light in vacuum (c) to the speed of light in a medium (v) is defined as refractive index (μ) of that medium.
\(\mu=\frac{c}{v}\)