Page 134 - Physics - XI

Q15. Under which circumstances are stationary waves formed?
Ans. Stationary waves are formed when a refl ected wave gets superposed with its incident wave.

Q16. Identify the nodes and anti-nodes in the string of your sonometer. (NCERT)
Ans. In a stationary wave, the regions of zero displacement and maximum strain are called nodes. While
the regions of maximum displacement and zero strain are called anti-nodes.

Q17. Keeping the material of wire and tension fi xed, how will the resonant length change, if the
diameter of the wire is increased? (NCERT)
Ans. Keeping the material of a wire and tension fi xed, if the diameter of the wire is increased, then the
resonant length of the wire will decrease as we know that

v 1 T v 1 and L 1 .
LD D D

Q18. What is the ratio of the fi rst three harmonics produced in a stretched string fi xed at the two
ends? (NCERT)
Ans. The ratio of the fi rst harmonics produced in a stretched string fi xed at the two ends is
v : v : v = 1 : 2 : 3 ______
3
1
2
EXPERIMENT - 10

Aim
To fi nd the speed of sound in air at room temperature using a resonance tube by two resonance positions.

Apparatus and Materials Required
Resonance tube apparatus, two tuning forks of known frequencies, a rubber pad, water in a beaker, a
plumb line, a thermometer, and a set-square

Description of Apparatus
Reservoir
Tuning fork S
A 0 A A
D 10 R l = λ
1 4
20 D
D
30 l = 3λ
4
2
40
50 P
60
E
70
80
B 90
100 T

Rubber tube

Levelling screw
S S

Fig. 10.1: Resonance tube apparatus
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