**Solution: **For the closed pipe,

Similarly, v = fλ ⇒ f = v/λ. Put in the above equation,

And for open pipe,

So f^{’} = v/λ^{’} now implies,

(11)If the amplitude of a wave is doubled, then its intensity is,

(A) Doubled | (B) Halved | (C) __ Quadrupled__ | (D) One-fourth |

**Explanation:** Intensity of a wave is proportional to the amplitude of the wave. So when the amplitude doubles, intensity is quadrupled (i-e, becomes 4 times).

12. A sound source is moving towards a stationary listener with 1/10 of the speed of the sound. The ratio of apparent to real frequency is:

(A) 11/10 | (B) (11/10)^{2} | (C) (9/10)^{2} | (D) __10/9__ |

**Solution:** The apparent frequency is given by the relation,

[See question 9 (1).]

The ratio of frequencies is, therefore,

(From the above equation)

Put the values

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2nd ka ans A hona chahiye?.

students

Amazing job 👍

Thank you, Khan.

Sir.

Intensity of wave is proportional to the square of the amplitude of wave.

Not only amplitude of wave.

We know that waves carry energy so after interference what happens to their energy in both constructive as well as destructive interference

Also in stationary waves what happens to the energy possessed by the waves