Which of the following materials conducts heat well?
a. metal
b. plastic
c. wood
d. glass

Answer : The correct option is, (a) metal

Explanation :

Conductors : Conductors are those in which the electric current can flow easily.

Insulators : Insulators are those in which the electric current can not flow.

Most of metals are conductors. That means it a good conductor of  heat and electricity.

The non-metals are insulators. That means it is a bad conductor of heat and electricity.

From the given options, metal conduct heat well. While the other options, plastic, wood and glass does not conduct heat well.

Hence, the material conducts heat well is, metal.

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.