# Are the sun rays incident on earth's surface parallel to good approximation?

If so how can an image of the sun be formed using a pinhole camera (for e.g. sun diameter estimate), the rays incident on the pinhole can't all be parallel and at least for this case the approximation si not valid, right ?

• Ok, I have edited the question to be more straightforward type now. – miquo Aug 31 '17 at 12:42
• I think the title's improved, but the first version wasn't a list question - it was perfectly acceptable by the rules of this site. Anyhow, you have a good answer already. – WetSavannaAnimal Aug 31 '17 at 23:50

• The rays traveling from the same point on the Sun to different points on the Earth are not precisely parallel either. However, the angle between them is much, much smaller. For example, the rays hitting the opposite sides of a lens with diameter 10 cm differ in angle by $$\theta \approx \frac{\text{diameter of lens}}{\text{Earth-Sun distance}} = \frac{ 10 \text{ cm}}{150 \text{ million km}} = 6.7 \times 10^{-13} \text{ radians} = 4 \times 10^{-11} \text{ degrees}.$$