Question

Two waves having same velocity enter electric and magnetic fields respectively. If ${\lambda }_1$and${\lambda }_2$ are their wavelengths as they move in the fields, then

• A. ${\lambda }_1,{\lambda }_2$ are constants
• B. ${\lambda }_1$ and ${\lambda }_2$ are variable
• C. ${\lambda }_1$ is variable ${\lambda }_2$ is constant
• D. ${\lambda }_2$ is variable, ${\lambda }_1$ is constant

Answer 1

The correct option is B ${\lambda }_1$ and ${\lambda }_2$ are variable

Velocity of a wave is given by:

$v=\frac{E}{B}$

Hence wave velocity change in both the cases.

Frequency of the wave remains the same.

Using $v=f\lambda$, it can be concluded that both ${\lambda }_1$ and ${\lambda }_2$ are variable.