## University Physics with Modern Physics (14th Edition)

The new amplitude would be $B\sqrt{2}$.
Equation 32.29 can be used to give the intensity in terms of the magnetic field amplitude. $$I=\frac{E_{max}B_{max}}{2\mu_o}$$ We use the fact that $E_{max}= cB_{max}$ $$I=\frac{cB_{max}^2}{2\mu_o}$$ If the intensity is doubled, the magnetic field amplitude is multiplied by $\sqrt{2}$.