Two mirrors in a He$-$Ne laser are spaced apart by $25\mathrm{.}0$ cm $.$

a$)$ What is the longitudinal mode spacing?

b$)$ The bandwidth of the gain curve is approximately $1300$ MHz $.$ What is the number of possible lasing frequencies?

c$)$ Now the mirrors are spaced apart by $30\mathrm{.}0$ cm $.$ Does this result in more or less possible lasing frequencies? Why?

Two mirrors in a He$-$Ne laser are spaced apart by $25\mathrm{.}0$ cm $.$

a$)$ What is the longitudinal mode spacing?

b$)$ The bandwidth of the gain curve is approximately $1300$ MHz $.$ What is the number of possible lasing frequencies?

c$)$ Now the mirrors are spaced apart by $30\mathrm{.}0$ cm $.$ Does this result in more or less possible lasing frequencies? Why?