Band structure of energy levels in solids 

You absolutely cleared this up for me. I cant say thank you enough. This was a huge help. This topics are not easy to teach to non physics majors.

Good video. However, formula at 15:09 (and rest of vid) is confusing as you are using K and k to mean two different periodic things.

Thanks for this excellent video ,I almost totally understand this topic. but i have a question that what is the physical meaning of n in K=2(pi)n/Na, Does n means the state? Because I know that the horizontal axis (from the graph at 23:00) is related to the energy ,but what is related to the vertical axis. Mathematically , it shows that there are no solution for the cos(Ka) within =+-1 from some Z1 to Z2. Can I take this as there are no energy state in between E1 and E2 ( Where Z1=K1 a & (K1)^2=2mE1/h^2 ) . It will be my pleasure if you answer this question .Again,your videos are awesome and I like the way you explain things. It helps me a lot in physics.Thank you.

Hi Dr. Carlson! Thank you so much for the videos! Can you please do videos on Chapter 6 of Introduction to Quantum Mechanics by Griffiths?

Can you please do chapter 6 (Symmetries and Conservation Laws) from this book? I am really struggling with selection rules for vector operators. Or does anyone know any resources that may cover this chapter for this book? (Griffiths' Introduction to Quantum Mechanics)

great lecture

Don't insulators have completely full/completely empty energy bands? You made it sound like they are partially filled

This is gold