Light of wavelengths $\lambda$₁ and ${\lambda }_2$ is made incident successively on the surface of metal Light of wavelength ${\lambda }_1$ produces photo-electric effect whereas light of wavelength ${\lambda }_2$does not. Then interference is produced using these light sources, the fringe widths0 obtained are ${\beta }_1$ and ${\beta }_2$ respectively, then

• A

  ${\mathrm{\beta }}_1>{\mathrm{\beta }}_2$

• B

  ${\mathrm{\beta }}_1<{\mathrm{\beta }}_2$

• C

  ${\mathrm{\beta }}_1={\mathrm{\beta }}_2$

• D

  none of these