To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. Mathematically it can be described as,

Here,
= Frequency of Source
= Speed of sound
f = Frequency heard before slowing down
f' = Frequency heard after slowing down
v = Speed of the train before slowing down
So if the speed of the train after slowing down will be v/2, we can do a system equation of 2x2 at the two moments, then,
The first equation is,



Now the second expression will be,



Dividing the two expression we have,

Solving for v, we have,

Therefore the speed of the train before and after slowing down is 22.12m/s
Answer:
except ii and iii
Explanation:
The angle of reflection is the angle to the normal the white rays strikes the water surface and it is the incidence angle. Since the white light is moving from less dense medium to a denser medium or a medium with a higher refractive index; the angle of refraction will be less than 30 degrees. Total internal reflection cannot occur because the white light is traveling from a less dense medium to a denser medium.
It is wavelength i think so!!!!
Answer:
not true because the mass from the heavy car will cause it to damage more
Explanation: