Radial function in Spherical potential well

[Swatch]

Homework Statement

A Spherical potential which is
0 for 0<r<a
Vo for r>a

Find the condition for bound states, for the radial function with l=0
Plot the result.

The Attempt at a Solution

I have gotten the equation

- tan(ka)=k/lambda
where k is the wavenumber for the wave inside the well and lambda is the wavenumber for the wave outside the wave.
I know these kind of equation have to be solved graphically or numerically. I have a similar equation solved graphically in my textbook but I don't understand it. Can anyone please help me and give me a hint to how to solve this transcendental equation?

 

[cks]

You just have to plot the two equations tan(ka) and k/lambda in a single graph. The intersection point between the function tan(ka) and the straight line k/lambda is the answer you need.

 

[Avodyne]

Except it's not a straight line, because lambda depends on k.

 

[cks]

I see. Thanks, Avodyne.

Then you have to plot of the graph of tan(ka) and k/lambda=k^2/2pi.

 

[Swatch]

I see. Thanks