Question

A student shakes a 5 m long slinky held at both ends, producing standing waves. Which of the following wavelengths did he fail to produce? a) 3.3 m b) 10 m c) 5 m d) 20 m e) 2.5 m

Answer 1

For standing waves, the length of the slinky must be equal to interger multiple of half the wavelength of the wave on the string. We have nodes at the end of the string. The distance between neighboring nodes is . Thus, we should have

, where n is an integer.

For the cases where , we get an integer if we substitute the wavelength and calculate n.

For 3.3 m and 20 m wavelength, we don't get an integer n. So, the student fails to produce 3.3 m and 20 m wavelength.