# If a strong diffraction peak is observed when electrons are incident at an angle ‘i’ from the normal to the crystal planes with distance ‘d’ between them (see figure), de Broglie wavelength $\lambda_{dB}$ of electrons can be calculated by the relationship (n is an integer)
( A ) $d\; sin\; i = n\lambda_{dB}$
( B ) $d\;cos\; i = n\lambda_{dB}$
( C ) $2d\; cos\; i = n\lambda_{dB}$
( D ) $2d\; sin\; i = n\lambda_{dB}$