Elliptical galaxies, such as M87 (left), have very little gas and dust. Because gas and dust are found in the clouds that are the birthplaces of stars, we should expect to see very few young stars in elliptical galaxies. In fact, elliptical galaxies contain primarily old, red stars (also known as Population II stars).
Elliptical galaxies vary widely in size. Both the largest and the smallest known galaxies are elliptical. Very large elliptical galaxies can reach 300 million light years in diameter. Dwarf ellipticals, which are very common, may contain only 1/100,000th as many stars as the Milky Way!
As light is an electromagnetic wave that causes sensation of sight.
Every electromagnetic wave has electrical and magnetic components in it which are perpendicular to the direction of propagation of wave.
The electrical and magnetic components are mutually perpendicular to each other in an electromagnetic wave.
The speed of light in vacuum is c=3\times 10^{8}\ m.s^{-1}, which decreases when it passes through a matter (precisely a transparent medium) which allows the passage of light through it. When the light passes through some transparent matter then its speed decreases as compared to the speed of light in vacuum.
if an object travels in a straight line and its velocity increases or decreases by equal amounts in equal intervals of time, then the acceleration is said to be uniform.
