Answer:
A

B

Step-by-step explanation:
From the question we are told that
The wavelength is
The angle of first bright fringe is
The order of the fringe considered is n =1
Generally the condition for constructive interference is
=>

=>

Converting to cm

Generally the number of grating pre centimeter is mathematically represented as

=>

=>

Considering question B
From the question we are told that
The first wavelength is
The second wavelength is
The order of the fringe is

The grating is

Generally the slit width is mathematically represented as

=>

=>

Generally the condition for constructive interference for the first ray is mathematically represented as
=>
=>
![\theta_1 = sin^(-1) [( 2 * 650 *10^(-9) )/( 2*10^(-6))]](https://img.qammunity.org/2021/formulas/physics/college/tjghxvpreyqzoo8xrscdaliwt8ilremhfg.png)
=>

Generally the condition for constructive interference for the second ray is mathematically represented as
=>
=>
![\theta_2 = sin^(-1) [( 2 * 420 *10^(-9) )/( 2*10^(-6))]](https://img.qammunity.org/2021/formulas/physics/college/h8egg4r9cgzkwe1d9tc2nbo3mxus7p8nli.png)
=>

Generally the angular separation is mathematically represented as

=>

=>
