Question

A narrow beam of monochromatic
light is incident normally on a
diffraction grating Third-order diffracted
beams are formed at angles of
45° to the original directions. What
is the highest order of diffracted
beam produced by this grating?
a)3rd
b)5th
c)4th
d)6th​

Answer 1

Explanation:

Given A narrow beam of monochromatic light is incident normally on a

diffraction grating Third-order diffracted  beams are formed at angles of

45° to the original directions. What  is the highest order of diffracted

beam produced by this grating?

• The angle φ has diffracted light and is given by d sinφ = pλ
• Now d is the grafting period, p is the order of diffraction and λ is wavelength of incident light.
• Now p max = d sinφ max / λ
• The diffracted beam is formed at an angle of 45 degree.
•                      So d sin 45 = 3λ
•   We can write this as  d/λ = 3 / sin 45
•                                   = 3 / 1 / √2
•                                   = 3√2  
•                                   = 4.242
• Now we need to find the highest order of diffraction.
• So  p max = d sin φ / λ
•                 = 4.24 (since mod sin φ <=1)
•                = 4

Reference link will be

https://brainly.in/question/15766710