Explanation:
It is given that,
Wavelength of red laser light,
The second order fringe is formed at an angle of,
For diffraction grating,
, n = 2
The wavelength λ of light that creates a first-order fringe at 22 is given by :
Hence, this is the required solution.
The book's vertical position in the air is
where . It reaches the ground when
, at a time
such that
So it takes the book 4 seconds to reach the bottom. The given initial velocity is irrelevant since it only has a horizontal component; vertically, the book is starting from rest.