A particle of mass `m` projected horizontally with velocity `u`. if it makes an angle `theta` with the horizontal after some time, then at that instant, its be Broglie wavelength is

Explanation

For a projectile horizontal component of velocity is constant.
`:.v_(x)=u_(x),V cos theta=u`
`:.` De Broglie wavelength,`lambda=h/(mv)=(h cos theta)/(mu)`