When I ride the train, the song of the train whistle is an example of the Doppler Effect. Because a train is at the center of sound waves it produces, which radiate in concentric circles around it, there is no difference between the sound heard by someone on the platform, and the sound of the train as heard by someone standing behind the caboose.
Answer:
1. A solid can diffuse into a liquid, but a solid cannot diffuse into another solid.
3. A liquid can diffuse into another liquid.
4. A gas can diffuse into another gas.
Explanation:
When an object is in liquid or gas form, they can easily move and spread. This is because the molecules are packed loosely. Since they can move freely, diffusion on and into gas/liquid can be easily achieved.
Solid form can diffuse into liquid too. Seawater is mostly made of water and solid salt. But diffusing a solid into a solid is not possible since the molecule is tightly packed and barely moves. The diffusion might be happening, but at a really slow rate that we can assume it is not.
Answer:
A

B

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} [\frac{ 2 * 650 *10^{-9} }{ 2*10^{-6}}]](https://tex.z-dn.net/?f=%5Ctheta_1%20%3D%20sin%5E%7B-1%7D%20%5B%5Cfrac%7B%202%20%2A%20%20%20650%20%2A10%5E%7B-9%7D%20%7D%7B%202%2A10%5E%7B-6%7D%7D%5D)
=> 
Generally the condition for constructive interference for the second ray is mathematically represented as
=>
=> ![\theta_2 = sin^{-1} [\frac{ 2 * 420 *10^{-9} }{ 2*10^{-6}}]](https://tex.z-dn.net/?f=%5Ctheta_2%20%3D%20sin%5E%7B-1%7D%20%5B%5Cfrac%7B%202%20%2A%20%20%20420%20%2A10%5E%7B-9%7D%20%7D%7B%202%2A10%5E%7B-6%7D%7D%5D)
=> 
Generally the angular separation is mathematically represented as

=> 
=> 