Calculating 2nd and 3rd Resonant Lengths

[soulja101]

Homework Statement

The 1st rensonat length of a closed air column occurs when the length is 30.0cm. what will the send ond and third be?

Homework Equations

I did the pattern thign like 3/4 but i got the wrong answer.

The Attempt at a Solution

i multplied the legth 3/4 but i got the wrong answer.

 

[joemok]

Second = 30.0*3=90.0 (cm)
Third= 30.0*5 = 150.0(cm)
u can draw graphs to know why.

 

[andrevdh]

A node is situated at the closed end an antinode at the open end. The "smallest structure" of the wavelength that can accommodate this is a quarter wavelength.Which means that the wavelength is 120 cm. The next waveform will be three quarters of a wavelength (again a node at the closed end and an antinode at the open end).