Match the following examples of energy with the primary form of energy exhibited. friction: nuclear power plant: toaster element: welding torch: eraser sitting on a desk edge: light bulb: campfire: moving car: lump of coal in a storage bin: stick of tnt: options are nuclear, heat, kinetic, potential, light, and solar energy

The primary energy exhibited is:

friction:  Heat energy

Due to friction. there is heat loss in mostly all machines.

nuclear power plant:  Nuclear energy

In nuclear power plant, fission or fusion of radio-active substances produces large amount of nuclear energy.

toaster element:  Heat energy

Heat energy is produced in the toaster when electricity passes through the element. This is used to heat the toasts.

welding torch:  Heat energy

The heat energy produced in the welding torch is used in welding.

eraser sitting on a desk edge:  Potential energy

Potential energy is possessed by a body due to virtue of its height.

light bulb:  Heat energy and light energy.

The element inside the bulb gets heated first and then light energy is produced.

campfire:  Heat energy

Heat is produced and then light energy in case of campfire.

moving car:  Kinetic energy

A moving body has kinetic energy.

lump of coal in a storage bin:  Potential energy

A lump of coal in a storage bin has potential energy.

stick of TNT: potential energy

Stick of TNT is formed of explosive mixture. It contains potential energy.

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.