Sounds waves travel at `350m//s` through a warm air and at `3500m//s` through brass. The wavelength of a `700 Hz`. Acoustic wave as it enters brass from warm air

Options

A. decreases by a factor `10`
B. increases by a factor `20`
C. increases by a factor `10`
D. decreases by a factor `20`

Answer

C

Explanation

Here, `upsilon_(air)==350ms^(-1),v_(brass)=3500ms^(-1)`
When a sound wave goes from onoe medium to another medium, its frequency `(v)` remains the same.
As, frequency `v=(velocity)/(wavel e ng th)=(upsilon)/(lambda)`.
Since `v` remains the same in both the media , so
`(upsilon_(air))/(lambda_(air))=(upsilon_(brass))/(lambda_(brass))` or ` lambda_(brass)=lambda_(air)xx(upsilon_(brass))/(lambda_(air))`
`=lambda_(air)xx(3500)/(350)=10lambda_(air)`