1.Round off the following measurement to the three significant figures. 1.296 g. 2. How many significant figures are there in the following measurement? 2020 g.

3.Round off the following measurement to the three significant figures. 5.658 grams

Explanation:

1) Significant figure means the amount of figure we are interested in. Note  that 0 is insignificant. For example 30 is a one significant figure i. e the only figure of interest is 3.

Given  the figure 1.296 g, as we can see, there are initially for figures in the value. This means we are to eliminate one to make it 3. To do that we will remove the 6 at the back by round it up to 1 and add it to the value of 29 preceding it to give 30. The figure will become 1.30 (to 3sf).

Note that only values greater than 4 are rounded up to 1 and added to the preceding value

2) Given the figure 2020, the number of significant figures present is 3 significant figure. Note that all zeros at the end of a value are considered insignificant hence the only significant value here is 202 (which is 3 sig fig.)

3) For the figure 5.658, the value to 3sf is 5.66 (Note that the value of 8 at the end is rounded up to 1 and added to 65 to make it 66). This is as explained in the first answer above.

absorption lines are where light has been absorbed by the atom thus you see a dip in the spectrum whereas.

emission spectra have spikes in the spectra due to atoms releasing photons at those wavelengths.

explanation:

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.