# B Are the Sun's rays reaching us always parallel?

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1. Dec 5, 2017

### jbriggs444

A concave lens? That won't focus. That'll disperse. In any case, the image of the sun will not magically turn into a point and will not collimate like a laser.

2. Dec 6, 2017

### Drakkith

Staff Emeritus
This is half wrong, as has already been pointed out multiple times in this thread. The light rays from any single point on the Sun are extremely close to parallel, which is exactly what the OP's book is talking about when it says Sunlight is parallel.

3. Dec 11, 2017

### B_iswas

1. They’re near parallel — but not parallel. sure, perspective intensifies their otherwise minuscule and imperceptible angle, but they’re not emanating from an infinite planar light source… they’re radiating from the sun.

2.
Anyone can see the angular width of the Sun so that isn’t of interest, but from any part of the Sun the light is virtually parallel.
however, the Sun’s rays received by Earth are converging.

At the time, the edges of the shadows very clearly diverge (and get blurry). This is due to the Sun appearing ~0.53° in the sky. Just think about it, the light from the far edges of the sun are very clearly NOT parallel with each other.

4. Dec 11, 2017

### A.T.

The shadows in that picture converge due to perspective (if that is the Sun and the poles are on Earth).

5. Dec 11, 2017

### Staff: Mentor

He's referring to the fact that each shadow has sides that are not parallel, not the perspective between the two...

...though I still disagree that the answer can be stated so simply. From a point on each "side" (limb) of the sun emerge photons/rays covering about 180 degrees of arc; diverging. This enables some of the rays to converge when considered in certain ways from earth. So I would say the statement "the Sun’s rays received by Earth are converging" is oversimplified at best.

6. Dec 11, 2017

### Drakkith

Staff Emeritus
This is incorrect. Converging and diverging light refer to light that comes from a single point, not from light that is emitted from different points. The Sun's light is diverging as it spreads out into space, not converging.

Since people don't want to read anything that's already been written or make sure their information is correct, I think it's time to close this thread.