Answer:
do you mean stages or branches
Refraction is a phenomenon which results when a ray of light enters from one medium to another medium. When a ray of light enters from denser medium to rarer medium, it bends away from the normal. The laws of refraction are: The incident ray, the refracted ray and the normal all lie in the same plane.
Complete Question
A commuter train passes a passenger platform at a constant speed of 39.6 m/s. The train horn is sounded at its characteristic frequency of 350 Hz.
(a)
What overall change in frequency is detected by a person on the platform as the train moves from approaching to receding
(b) What wavelength is detected by a person on the platform as the train approaches?
Answer:
a

b

Explanation:
From the question we are told that
The speed of the train is 
The frequency of the train horn is 
Generally the speed of sound has a constant values of 
Now according to dopplers equation when the train(source) approaches a person on the platform(observe) then the frequency on the sound observed by the observer can be mathematically represented as

substituting values


Now according to dopplers equation when the train(source) moves away from the person on the platform(observe) then the frequency on the sound observed by the observer can be mathematically represented as

substituting values


The overall change in frequency is detected by a person on the platform as the train moves from approaching to receding is mathematically evaluated as



Generally the wavelength detected by the person as the train approaches is mathematically represented as


