The h line in calcium is normally at 396.9 nm. however, in a star's spectrum, it is measured at 398.1nm. how fast is the star moving and is it moving towards the earth or away from the earth? 1- 904.3 km/s away from the earth 2- 904.3 km/s towards the earth 3- 907.0 km/s towards the earth 4- 907.0 km/s away from the earth

As we know by Doppler's effect of light we have

here we will have

[tex}\frac{398.1 nm - 396.9 nm}{398.1 nm} = \frac{v}{c}[/tex]

here by solving above we have

here we have

since wavelength is increased so we can say that it is moving away

so correct answer is

1- 904.3 km/s away from the Earth

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 components of a vector are the parts of the vectors that are to each other.

b perpendicular