Question

A sound from a stationary siren is reflected by a high wall approaching with velocity u towards a stationary person. The siren emits the wave at frequency v travelling in air with speed V. Find the apparent frequency of wave reflected by wall and number of beats heard per second. Siren and person both are on the same side of wall.

Solution

The apparent frequency of wave received by wall approaching the siren is,

<pre>uncaught exception: <b>mkdir(): Permission denied (errno: 2) in /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php at line #56mkdir(): Permission denied</b><br /><br />in file: /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php line 56<br />#0 [internal function]: _hx_error_handler(2, 'mkdir(): Permis...', '/home/config_ad...', 56, Array) #1 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php(56): mkdir('/home/config_ad...', 493) #2 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/FolderTreeStorageAndCache.class.php(110): com_wiris_util_sys_Store->mkdirs() #3 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/RenderImpl.class.php(231): com_wiris_plugin_impl_FolderTreeStorageAndCache->codeDigest('mml=<math xmlns...') #4 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/plugin/impl/TextServiceImpl.class.php(59): com_wiris_plugin_impl_RenderImpl->computeDigest(NULL, Array) #5 /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/service.php(19): com_wiris_plugin_impl_TextServiceImpl->service('mathml2accessib...', Array) #6 {main}</pre>

Wall reflects back the received wave.
Therefore the wall behaves like a source of wave emitting wave at a frequency v₁.
The wall is approaching the person.

Therefore, apparent frequency of reflected wave received by observer is,

straight v subscript 2 equals fraction numerator straight V over denominator straight V minus straight u end fraction straight v subscript 1 space equals space fraction numerator straight V plus straight u over denominator straight V minus straight u end fraction straight v

The number of beats heard per second is given by,

space space space space space space space space straight b equals straight v subscript 2 minus straight v equals fraction numerator 2 straight u over denominator straight V end fraction straight v

For Daily Free Study Material Join wiredfaculty

Mechanical Properties Of Fluids

Some More Questions From Mechanical Properties of Fluids Chapter

What are different types of wave motions?

Define transverse wave motion.

Define longitudinal wave motion.

Which of the two waves - elastic waves or electromagnetic waves does need any material media for its propagation?

What is sound?

How sound is produced?

Can sound travel in vacuum?

Can two persons hear each other on the moon? Explain.

Can electromagnetic wave propagate in vacuum?

Can we listen in vacuum?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Phone Number

Email Address

Location