Tag: acoustics

Quizzes (14) Questions (34)

Questions Related to acoustics

Multiple choice physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

In a room two walls are at a distance of 159 m, then

  1. no echo will be heard

  2. an echo can be heard

  3. no sound will be heard

  4. none
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Rooms having walls less than 17.2 m away from each other, no echo can be heard. here, 159 m is greater than 17.2 m. So an echo will be heard if other conditions are fulfilled.

Multiple choice physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

When echo is heard?

  1. If the time interval between original sound and reflected sound is more than 1/10s.

  2. If the time interval between original sound and reflected sound is less 1/10s.

  3. If the time interval between original sound and reflected sound is less than 1/120s.

  4. If the time interval between original sound and reflected sound is 1/120s
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If the time interval between original sound and reflected sound is more than $\frac{1}{10}\,s$, then the original sound and the reflected sound can be clearly heard. This reflected sound is known as echo.

Multiple choice physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

An echo is heard on a day when temperature is about $44^0$C. When will the echo be heard if the temperature falls to $80^0$C?

  1. Sooner

  2. Later

  3. At the same time

  4. No echo will be heard
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Time, after which an echo is heard is given by $t = \dfrac {Distance}{Speed \ \ of \ \ sound \ \ in \ \ air}$
Therefore, since speed of sound in air increases with the increase in temperature, so the time after which echo will be heard decreases. Hence, echo will be heard, sooner than the echo heard when temperature near $44^0C$

Multiple choice physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

For the production of an echo,size and nature of the obstacle should be :

  1. small and rigid respectively

  2. small and soft respectively

  3. large and rigid respectively

  4. large and soft respectively
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For the production of an echo, the reflecting surface or the obstacle should be rigid such as building, hill, cliff. Echo can be produced if the size of the obstacle reflecting the sound is quite large.

Multiple choice physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

In a room two walls are at a distance of 159 m. Then :

  1. no echo will be heard

  2. an echo can be heard

  3. no sound will be heard

  4. none of these are true
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In rooms having walls less than 17.2m away from each other, no echo can be heard. Here,walls of the room are at a distance of 159 m, much greater than 17.2m. So an echo will be heard if other conditions are fulfilled.

Multiple choice physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

A sponge is kept at a distance of 19m from a source of sound.

  1. No echo will be heard

  2. An echo can be heard

  3. No sound will be heard

  4. None of the above is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The minimum distance in air between the observer and the obstacle for an echo to be heard clearly is nearly 17.2m. This condition is followed here but for the production of an echo, the obstacle should be rigid.

Multiple choice physics acoustics conditions for hearing echo echo reflection of sound and echo ultrasound and its applications

The minimum distance to hear a clear echo is (V is the velocity of sound)

  1. 2V/5

  2. 5V/2

  3. V/20

  4. 5V
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Minimum frequency to the human ear is 20
$\therefore T= \dfrac {1} {F}$
$T=\dfrac{1} {20}$
$d= V \times t$
$d= V\times \dfrac {1} {20}$
$\therefore$ The minimum distance is$ \dfrac {V} {20}$, where V is speed of the sound.