# I Am I crazy or is my book wrong?

#### yjl

Hey all,

My book says/does the following.

Use the following equation for a plane wave

Fill it in the klein-gordon equation

To get

Which results in

Is this right? I got something different and no matter how hard I try I can't replicate the same answer. I've gotten the last equation, but without the c to the power of 4. I also feel like they just flat out forgot μ in the third equation.

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#### jasonRF

Gold Member
I've gotten the last equation, but without the c to the power of 4.
It should be $\omega^2 = c^2 k^2 + c^2 \mu^2$, where $k^2 = k_x^2 + k_y^2 + k_z^2$; if this is what you got then you did it correctly
I also feel like they just flat out forgot μ in the third equation.
Yes.

By the way, what book is this?

Jason

#### yjl

It should be $\omega^2 = c^2 k^2 + c^2 \mu^2$, where $k^2 = k_x^2 + k_y^2 + k_z^2$; if this is what you got then you did it correctly

Yes.

By the way, what book is this?

Jason
Yes, thank you!

That's what I kept ending up on. :-)

It's not a book that's publicly available. It's my professor's LaTeX book that he wrote for the course. He did say that it's still very much a work in progress, but still..

#### jtbell

Mentor
It's my professor's LaTeX book that he wrote for the course
I hope you'll tell him about this, politely. If it were me, I would appreciate the feedback.

#### yjl

I hope you'll tell him about this, politely. If it were me, I would appreciate the feedback.
Yes, I e-mailed him. Wonder if he'll appreciate or find it annoying to be honest

#### ZapperZ

Staff Emeritus
2018 Award
Yes, I e-mailed him. Wonder if he'll appreciate or find it annoying to be honest
If he finds it annoying that someone pointed out a mistake in his text, then he has no business being a physicist, or an educator for that matter.

Zz.

"Am I crazy or is my book wrong?"

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