The destructive interference formula for diffraction grating problems is
.
<h3>What is the definition of destructive interference?</h3>
Destructive interference happens when the maxima of two waves are 180° out of phase a positive displacement of one wave is canceled exactly by a negative displacement of the other wave.
The formula for brighter patches resulting from constructive interference and darker patches resulting from destructive interference in a diffraction grating is:

The grating spacing is denoted by d, the angle of light is denoted by a the fringe order is denoted by n, and the wavelength is denoted by
.
The destructive interference formula is now based on the fact that destructive interference occurs between the fringes.
Hence the destructive interference formula for diffraction grating problems is
.
To learn more about destructive interference refer to the link;
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Explanation:V.R of a lever is 3 means effort distance of the lever is 3 times more than the effort distance of the load. ... Efficiency of a lever is 60% means 40% of the energy is wasted due to friction as no machine is Friction less.
Momentum = mass x velocity
Momentum = 10.5 x 3
Momentum = 31.5 kgm/s