A metallic ring of mass 1 kg has moment of inertia 1 kg m² when rotating about one of its diameters. It is molten and remoulded into a thin uniform disc of the same radius. How much will its moment of inertia be, when rotated about its own
axis.

The moment of inertia of disc about own axis is 1 kg-m².

Explanation:

Given that,

Mass of ring m= 1 kg

Moment of inertia of ring at diameter

The radius of metallic ring and uniform disc both are equal.

So,

We need to calculate the value of radius of ring and disc

Using theorem of perpendicular axes

Put the value into the formula

Put the value of moment of inertia

Put the value of M

So,

We need to calculate the moment of inertia of disc about own axis

Using formula of moment of inertia

Put the value into the formula

Hence, The moment of inertia of disc about own axis is 1 kg-m².

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.