Derive the relationship v = λ × f .

Let the velocity of the wave be v , wavelength λ and frequency be f . Consider a point on the crest of the wave. This crest will reach at the position of the consecutive crest when it covers a distance equal to λ meter . The time taken in this shift will be equal to the time period T = 1 f of the wave. Using the definition for velocity of wave: v = distance covered time - interval = λ T = λ 1 / f = λ × f The above expression is the required relationship.

What is an echo? How is it produced? What should be the minimum distance(in air, at 20 ∘ C )between the observer and the obstacle for an echo to be heard clearly?(The speed of sound at 20 ∘ C = 343 m / s )

The sound returning towards the source after suffering reflection from a distant obstacle(a wall, a hill, a row of buildings etc.) is called an echo. Since the sensation of sound persists for 1 10 s hence, if the sound after reflection returns after this time-interval an echo is heard distinctly. This time interval depends on the speed of sound in the medium and the distance between the source and the reflecting wall. The speed of sound in air at 20 ∘ C = 343 m / s For an echo to be heard distinctly t ≤ 0 . 1 s Let the distance between the source and the obstacle be d meter . Then the distance covered by the sound: 2 d ≤ 343 × 0 . 1 = 34 . 3 m ⇒ d = 17 . 15 m The required distance is 17 . 15 m .

E M B I B E

Physics>Chapter 6 - Sound>PERIODIC TEST

Dr. S K Jain and Dr. Shailesh K Jain Solutions for Chapter: Sound, Exercise 7: PERIODIC TEST

Author:Dr. S K Jain & Dr. Shailesh K Jain

Dr. S K Jain Physics Solutions for Exercise - Dr. S K Jain and Dr. Shailesh K Jain Solutions for Chapter: Sound, Exercise 7: PERIODIC TEST

Attempt the practice questions on Chapter 6: Sound, Exercise 7: PERIODIC TEST with hints and solutions to strengthen your understanding. Physics solutions are prepared by Experienced Embibe Experts.

Questions from Dr. S K Jain and Dr. Shailesh K Jain Solutions for Chapter: Sound, Exercise 7: PERIODIC TEST with Hints & Solutions

EASY

9th CBSE

IMPORTANT

Physics>Chapter 6 - Sound>PERIODIC TEST>Q (i)

What is meant by quality of sound?

MEDIUM

9th CBSE

IMPORTANT

Physics>Chapter 6 - Sound>PERIODIC TEST>Q (j)

How do sound waves differ from radio waves?

MEDIUM

9th CBSE

IMPORTANT

Physics>Chapter 6 - Sound>PERIODIC TEST>Q (k)

Derive the relationship $v = λ \times f$ .

MEDIUM

9th CBSE

IMPORTANT

Physics>Chapter 6 - Sound>PERIODIC TEST>Q (l)

How does a sound wave propagate?

MEDIUM

9th CBSE

IMPORTANT

Physics>Chapter 6 - Sound>PERIODIC TEST>Q (n)

Derive mathematical equation describing the relationship between wave velocity, wavelength and frequency.

MEDIUM

9th CBSE

IMPORTANT

Physics>Chapter 6 - Sound>PERIODIC TEST>Q (o)

What is an echo? How is it produced? What should be the minimum distance(in air, at $20^{\circ} C$ )between the observer and the obstacle for an echo to be heard clearly?(The speed of sound at $20^{\circ} C = 343 m / s$ )