# NCERT Class-9 Science Solutions: Chapter 12-Sound Part 4

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Question 18:

Represent graphically by two separate diagrams in each case

1. Two sound waves having the same amplitude but different frequencies?

2. Two sound waves having the same frequency but different amplitudes.

3. Two sound waves having different amplitudes and also different wavelengths.

(A) Two sound waves having same amplitude but different frequencies

(B) Two sound waves with same frequency and different amplitudes

(C) Two sound waves having varying amplitudes and different wavelengths

Question 19:

Establish the relationship between speed of sound, its wavelength and frequency. If velocity of sound in air is, calculate

1. Wavelength when frequency is

2. Frequency when wavelength is

Question 20:

Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound. Mark the position of compression and rarefaction on this curve. Also define wavelengths and time period using this curve.