Physics - Sound Wave Question with Solution | TestHub

Paragraph:Two trains $A$ and $B$ are moving with speeds $20\mathrm{m}/\mathrm{s}$ and $30\mathrm{m}/\mathrm{s}$, respectively in the same direction on the same straight track, with $B$ ahead of $A$. The engines are at the front ends. The engine of train $A$ blows a long whistle. Assume that the sound of the whistle is composed of components varying in frequency from $f_1=800\mathrm{Hz}$ to $f_2=1120\mathrm{Hz}$, as shown in the figure. The spread in the frequency (highest frequency - lowest frequency) is thus $320\mathrm{Hz}$. The speed of sound in still air is $340\mathrm{m}/\mathrm{s}$.Question:The spread of frequency as observed by the passengers in train $B$ is