Advertisements
Advertisements
Question
Explain by giving a scientific reason.
We cannot hear the echo produced in a classroom.
Advertisements
Solution
- An echo is a sound produced when the original sound is reflected by the walls of a given room. For instance, in a small room If there are hard walls there will be an echo of sound bouncing off the wall but because the sound bouncing is so close to the original, it is harder to detect the echo produced.
- A room which is having a dimension greater than 17.2 m will produce an echo in that room.
- The dimensions of a classroom usually do not exceed 17.2 m, so echo is not produced in a classroom. So, in the case of a classroom, no echo is produced in a classroom.
APPEARS IN
RELATED QUESTIONS
An echo returned in 3 s. What is the distance of the reflecting surface from the source, given that the speed of sound is 342 m s−1?
Does sound follow the same laws of reflection as light does? Explain.
Explain why, the flash of lightning reaches us first and the sound of thunder is heard a little later.
What is the other name of a loud-hailer ?
Name the device which is used to address a small gathering of people.
Fill in the blank with suitable word :
Echoes are caused by the ...................... of sound.
On which day, a hot day or a cold day, an echo is heard sooner ? Give reason for your answer.
What is meant by 'reflection of sound' ? What type of surfaces are the best for reflecting sound ?
A man standing 825 metres away from a cliff (steep rock) fires a gun. After how long will he hear its echo ? Speed of sound in air is 330 m/s.
A man is kidnapped, blindfolded and imprisoned in a big room. How could the man tell if he was in : a bare room
An echo-sounder in a trawler (fishing boat) receives an echo from a shoal of fish 0.4 s after it was sent. If the speed of sound in water is 1500 m/s, how deep is the shoal ?
The frequencies of four sound waves are given below. Which of these sound waves can be used to measure the depth of sea by the echo method ?
Which of the following device does not work on the multiple reflections of sound waves ?
Answer the following question in your own words.
What is an echo?
Answer the following question in your own words.
What should be the dimensions and the shape of classrooms so that no echo can be produced there?
State two conditions necessary for hearing an echo.
______ allows bats to navigate through dark caves and find insects for food.
______ is an image obtained by the use of reflected ultrasonic waves.
Numerical problems:
An echo returned in 3s. What is the distance of the reflecting surface from the source given that the speed of sound is 330 ms-1?
