Selina solutions concise physics class 7 icse Solutions for Chapter 6 sound

Q1) A boy fires a gun and another boy at a distance of 1020m hears the sound of firing the gun 3s after seeing its smoke. Find the speed of sound.

Q2) A boy on a hill A fires a gun. The other boy on hiss B hears the sound after 4s. If the speed of sound is 330ms^{-1} find the distance the two hills

Q1) True and False

(a) Sound can travel in vacuum.

(b) Sound is a form of energy.

(c) Sound can only be produced by vibrating bodies.

(d) Larger is the amplitude, feeble is the sound.

(e) The frequency is measured in hertz.

(f) Loudness depends on frequency.

(g) Waveforms of two different stringed instruments can be the same.

(h) Female voice is shriller than the male voice.

(i) A ticking clock sound is heard late when heard through a metal.

Q2) Fill in the blanks

(a) Sound is produced when a body _\.

(b) The number of times a body vibrates in one second is called its __\.

(c) The pitch of a sound depends on its __\.

(d) Sound can travel in a ____\.

(e) We can hear sounds of frequency in the range of _______

(f) Sound requires a ______ for propagation.

(g) Sound travels faster in ____ than in liquids.

(h) The sound heard after reflection is _\.

(i) _____ produces sensation in ears.

Q3) Match the following

Q4) Select the correct alternative

(a) We can distinguish a shrill sound from a flat sound by its

1. Amplitude

2. Loudness

3. Pitch

4. None of the above

(b) We can hear sound of frequency ……………………………………

1. 10hz

2. 500 Hz

3. 100,000 Hz

4. 50,000 hz

(c) Sound cannot travel in …………………………………………………………………………

1. Gases

2. Liquids

3. Solids

4. Vacuum

(d) The minimum distance required between the source and the reflector so as to hear the echo in air is ……………………………………

1. 10m

2. 17m

3. 34m

4. 50m

(e) Wavelength is measured in ……………………………………………………………….

1. Kg

2. Second

3. Litre

4. Metre

(f) The speed of sound in water is ………………………………………………………………….

1. 332 m

2. 1500 m

3. 5000 m/s

4. 1000 m/s

(g) Sound travels the fastest in …………………………………………………………………….

1. Liquids

2. Solids

3. Gases

4. Vacuum

Q1) What do you mean by a vibratory motion?

Q2) What is sound?

Q3) How is sound produced?

Q4) Describe an experiment to show that each source of sound is a vibrating body.

Q5) Name two sources of sound.

Q6) How do we produce sound?

Q7) The bees do not have voice boxes. How do they produce sound?

Q8) Can sound travel a vacuum? Describe an experiment to explain your answer.

Q9) Describe an experiment to show that sound can travel in water.

Q10) Describe an experiment to show that sound can travel in a solid.

Q11) Can two people hear each other on moon’s surface? Give reason

Q12) What is a longitudinal wave?

Q13) Define the following terms:

Amplitude, Time period, Frequency

Q14) Write the audible range of frequency for the normal human ear

Q15) What are ultrasonics? Can you hear the ultrasonic sound?

Q16) What are infrasonics? Can you hear them?

Q17) How does a bat make use of ultrasonic waves to find its way?

Q18) Name the two characteristics of sound which differentiate two sounds from each other.

Q19) On what factor does the loudness of a sound depend?

Q20) How does the loudness of a sound depend on the vibrating area of the body?

Q21) The outer case of the bell in a temple is made big. Give reason

Q22) State the factors on which the pitch of a sound depends.

Q23) Differentiate between a high pitch sound and a low pitch sound

Q24) How does a man’s voice differ from a woman’s voice?

Q25) Name the characteristic which differentiates two sounds of the same pitch and same loudness

Q26) You recognise your friend by hearing his voice on a telephone. Explain.

Q27) A musician recognises the musical instrument by hearing the sound produced by it, even without seeing the instrument. Which characteristic of sound makes this possible.

Q28) Describe an experiment to show the production of sound having low and high pitch.

Q29) How does a musical playing on a flute change the pitch of sound produced by it?

Q30) Why are musical instruments provided with more than one string?

Q31) How can the pitch of sound produced in a piano be changed?

Q32) Explain why you can predict the arrival o fa train by placing your ear on the rails without seeing it.

Q33) Write the approximate speed of sound in (i) air (ii) water and (iii) steel

Q34) During a thunderstorm the sound of thunder is heard after the lightning is seen. Why?

Q35) Describe an experiment to estimate the speed of sound in air

Q36) Can sound travel through solids and liquids? In which of these two does it travel faster?

Q37) What do you mean by reflection of sound?

Q38) State one use of reflection of sound?

Q39) What is echo?

Q40) What minimum distance is required between the source of sound and the reflecting surface to hear an echo? Give reason.

Q41) List four substances which are good absorbers of sound.

Q42) List the measures that you will take when designing a sound proof room.