The spiral structure of the milky way can be explained by long lived quasi-static density waves<em>, </em><em>according to the lin-shu hypothesis. </em>Curiously, the waves of higher density gas and stars (seen as spiral arms) appear to remain static as stars move around the galaxy. This explained by assuming that the gravitational disturbances cause by the 'clumping' material in the arms does not affect the gravitational field of the galaxy as whole and is therefore negligible.
source: Astrophysicist
Answer:
B.electromagnetic spectrum
Explanation:
Electromagnetic spectrum is used to describe all of the wavelengths of light waves.Generally wavelength of the wave is denoted by λ.
Wavelength is the distance between two consecutive crest .Wavelength of the red color is minimum and wavelength of the violet color is maximum in the light spectrum.
So the answer is B.
Electromagnetic spectrum
<u>Answer</u>:
The greatest possible acceleration of the car is 
<u>Explanation</u>:



-------------(1)

----------------(2)
Solving the equation (1) and(2)








Next lets assume that the front wheels contact with the ground N_A = 0














Choosing the critical case



There are plant cells called chloroplasts, plants leave chloroplasts which have chlorophyll that capture and absorb light energy from the sun.