Wavefronts: Understanding Wave Optics

[Bheshaj]

What Is a wavefront? How can we interpret it?

 

[BvU]

How do you interpret it ? What have you found so far ?

 

[Bheshaj]

How do you interpret it ? What have you found so far ?

as per my book it is locus of all points oscillating in same phase. but i am not getting any sense of it from definition as to how to identify them and their structures.

 

[BvU]

Wording as in wiki. It's a description. When you are surfing you ride the crest of a wave: a wavefront. Do they have a structure ?

 

[Bheshaj]

Wording as in wiki. It's a description. When you are surfing you ride the crest of a wave: a wavefront. Do they have a structure ?

like if we through a stone in water the wavefront of water waves will have spherical structure as an example

 

[BvU]

Cultural issue: I would call that shape and reserve 'structure' for 'how it's built and with what'.
Other issue with 'identify': they don't have social security numbers.
Double trouble with 'how to identify them and their structures' .

Google is your friend: a wave is a propagating disturbance and from that I would loosely consider the wavefront as the locus of 'first arrivals'.

For identification some form of detection seems indicated and for shape you would need extended detection.

Shape is relative: for a lot of phenomena the plane wave concept is already adequate, for others you need a bit more (cylindrical, spherical).

 

[Bheshaj]

Cultural issue: I would call that shape and reserve 'structure' for 'how it's built and with what'.
Other issue with 'identify': they don't have social security numbers.
Double trouble with 'how to identify them and their structures' .

Google is your friend: a wave is a propagating disturbance and from that I would loosely consider the wavefront as the locus of 'first arrivals'.

For identification some form of detection seems indicated and for shape you would need extended detection.

Shape is relative: for a lot of phenomena the plane wave concept is already adequate, for others you need a bit more (cylindrical, spherical).

why does a point source produce spherical wavefront because waves are emitted in all the directions in 3 dimension

 

[BvU]

A disturbance proagates with a certain speed. If the medium is isotropic that speed will be the same in every direction, so after a given time the wavefront () has propagated over equal distances in all directions. The locus of points that have the same distance to a given origin is a spherical shell

 

[Bheshaj]

A disturbance proagates with a certain speed. If the medium is isotropic that speed will be the same in every direction, so after a given time the wavefront () has propagated over equal distances in all directions. The locus of points that have the same distance to a given origin is a spherical shell

got it , but can you please tell what will be the wavefront for converging and diverging rays and why?

 

[BvU]

You bring in 'rays' now. What are you asking ? What have you found so far and what is unclear ?

Rays are perpendicular to wavefronts, so:

Best I can think of is diverging $\leftrightarrow$ convex
and converging $\leftrightarrow$ concave (2nd picture in the link from post #4)

 

[vanhees71]

I wouldn't define "wave front" as the points of equal phase but rather as @BvU in #6: It's the boundary of the support of the wave. It's important to note that according to relativity that boundary cannot move faster than the speed of lightt in vacuo. Both phase velocity (i.e., the speed of points of equal phase) and group velocity (i.e., the speed of the center-of-energy) can exceed the speed of light without violating any causality constraints of relativity, and indeed that's what happens for light (electromagnetic waves) propagating in matter.