1
$\begingroup$

Today I notice very weird (for me) phenomenon, I was in open in evening in a garden , and looking at leaves of trees around me.

1.I see a yellowish glow of sunlight on it along with green colour of leaves.

But I have learnt that when sunlight fall on a colored object, every wavelength colour in spectrum of sunlight got absorbed by object and reflect only that wavelength colour of which colour object is! Example If I have a red ball , sunlight falling on it , every other colour from sunlight got absorb except red, which reflect into eye help us to identify colour of ball.

So if trees leaves are green ,and in evening sunlight is little yellowish(due to absenceof blue colour because if scattered away) , according to Me all colour should get absorb by green leaves except green so only colour from leaves visible should be green.

But there was a golden glow how, does sunlight reflect from rough leaf!

2 Same I notice with a red bulb on my ceiling it is making a rough concrete wall behind glowing red, but wall is black is colour. Again same doubt "if a particular colour object the all colour lights from spectrum from source except the one whose colour object is , than that black wall should absorb red colour . Glow should be visible only If light reflects from it , but that wall is black in colour , why it doesn't absorb red light from bulb . Same even if wall is green , pink etc. All the wavelength light should be absorb except the object's 'colour' one!

Please explain where I am having misconception?

Look

enter image description here

See here Apple and leaf absorb blue colour because it doesn'tmatch to apple colour. Shouldn't the black wall(or any colour) should absorb red light from bulb

$\endgroup$
1
  • $\begingroup$ I have seen this very thing happen before too. Mostly in AZ in the eveni ng sun with a strong golden sunset. The pine trees along the hwy that are dead absorb the golden sun light and look very golden. $\endgroup$ Aug 15, 2023 at 22:51

2 Answers 2

3
$\begingroup$

But I have learnt that when sunlight fall on a colored object, every wavelength colour in spectrum of sunlight got absorbed by object and reflect only that wavelength colour of which colour object is

This is a simplified explanation. Note that green leaves don't have a saturated green color. They are rather pale. This means that some of the non-green parts of the spectrum are also reflected, washing out the pure green to more natural color, as well as letting you see the spot of sunlight.

The exact color may be given by a reflectance spectrum. See a sample reflectance spectrum of a green leaf below (image source). The chlorophyll absorption peaks result in the reduction of reflectance at roughly $450\,\mathrm{nm}$ (blue) and $650\,\mathrm{nm}$ (red), and this is what gives you green color. But the absorption is far from complete, which reduces color saturation.

$\endgroup$
10
  • $\begingroup$ But ,in noon also this means some of the sunlight is reflected back ....but we don't notice it , simply we see a green color leaf. But as in morning or sunset when light is reddish yellow , we start seeing a golden patch. So why don't in noon we see white patches ? And only green color of leaf? $\endgroup$
    – user313211
    Oct 11, 2021 at 8:54
  • $\begingroup$ @SureshChandraPal that's because of chromatic adaptation. $\endgroup$
    – Ruslan
    Oct 11, 2021 at 9:06
  • $\begingroup$ What do u mean ,can u pls explainsir? $\endgroup$
    – user313211
    Oct 11, 2021 at 9:18
  • 1
    $\begingroup$ @SureshChandraPal you should make a clear distinction between color and frequency. The color of an object is composed of a lot of frequencies in different proportions. A green object will have more reflectance in the green range of the spectrum, but may have nonzero reflectance in other parts of the spectrum. In particular, if you look through a red filter at a leave lying on a wet soil, you'll see that the leave is brighter than the soil. This must mean that some red is reflected from the leave, so not all of it is absorbed. $\endgroup$
    – Ruslan
    Oct 11, 2021 at 10:59
  • 1
    $\begingroup$ @SureshChandraPal that's basically right. In the evening sunlight has much smaller amount of blue, and somewhat smaller amount of green, so you get a noticeable tint of orange in the reflected light. I.e. if at noon you get "small blue, large green, small red", then in the evening the reflected light is "almost no blue, some green, some red", and this looks like orange. $\endgroup$
    – Ruslan
    Oct 11, 2021 at 11:37
2
$\begingroup$

This is grazing incidence scattering. For perpendicular incidence predominantly green light is reflected. For grazing incidence all colors are reflected, as in the case of the air-glass interface. The reflectivity limit is unity independent of polarisation and color. Fresnel reflectance/transmittance for air to glass

See https://en.wikipedia.org/wiki/Fresnel_equations#Power_(intensity)_reflection_and_transmission_coefficients

$\endgroup$
1
  • $\begingroup$ Can u please elaborate it more? In a easy way , I m just a student I haven't study these in deep! $\endgroup$
    – user313211
    Oct 10, 2021 at 12:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.