41. Electric and magnetic forces can both make certain objects move. For example, a positively charged particle will repel another positively charged particle. Which of these is the best way for a student to demonstrate the same principle using magnets?

Place the north pole of a magnet next to the north pole of another magnet.

Explanation:

Looking at the comments, we can see that the options are:

Place the south pole of a magnet next to the north pole of another magnet.

Place the north pole of a magnet next to the north pole of another magnet.

First, we know that a positively charged particle will repel another positively charged particle.

The same thing happens for magnetic forces (usually we define a magnetic flow from the south pole to the north pole, so we can define the south pole as the "positive" and the north pole as the "negative", but this is only notation and do not really matter), a south pole of a magnet will repel another south pole of a magnet (and the same happens for the north poles)

Then the correct option is:

Place the north pole of a magnet next to the north pole of another magnet.

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.

the answer is a. hope this .