Today I am going to describe you about the red shift and blue shift of the white light. You are not going to see this phenomenon until you travel at the speed near the speed of light or until you see any object moving near the speed of light.
But you can experience the same phenomenon with sound. Have you ever heard the sound of vehicle sieren when it is moving towards you or moving away from you at high speed. You will noticed that when it is coming towards, then you will hear same sound with high pitch, but when it is going away from you then you will hear low pitch sound.
Well, why it happens?
As we know sound travels in the form of wave. When the vehicle is coming towards you, at that time the sound wave compresses, due to that compression of sound wave the wave-length of the sound wave get decrease due to which frequency get increased. But there is no change in its amplitude. ( It means 'db' remains constant ).
Similarly when vehicle is going away from you, then the sound wave get stretched due to which wave-length get get increase and frequency get decreased.
Come on the topic
Red shift: It is called as red shift because in this condition light coming from a source start looking red. When an object is moving away from an observer with the speed near the speed of light, then the electromagnetic wave (or light) start stretching ( not actually ) or its wave-length start increasing due to which it start looking red. Because when wave-length increases then frequency decreases. And as we know red light have low frequency and higher wave-length. So, it start looking red.
Blue shift: It is called as blue shift because in this condition light coming from a source start looking blue. When an object is moving towards an observer with the speed near the speed of light, then the electromagnetic wave (or light) start squeezing ( not actually ) or its wave-length start decreasing due to which it start looking blue. Because when wave-length decreases then frequency increases. And as we know blue light have high frequency and lower wave-length. So, it start looking blue.
How can we use this information.
When we see any blue light emitting body which is moving in space then we can say that, it is comming towards us. And when we see any red light emitting body which is moving in space then we can say that, it is going away from us.
