I dont understand why you cant see anything smaller than a wave length [or packet] of light?

Question

Please give a simple explanation.

Thanks

Answer 1

This is pretty much because this is exactly how we can see objects: when light bounces off of objects and "into" our eye.

Think of each "wave" of light as a pixel (or dot) on a tv screen. As each wave bounces off of something and into our eye, we collectively make a picture in our mind, just as we do when a bunch of little pixels are illuminated on a tv screen.

The size of each pixel determines how much detail we can see on the tv screen. The smaller the pixels, the more likely we can see things as incredibly small and detailed as the eyes of the spectators in a football game, like we notice on the freekn amazing HD tv screens.

On a normal tv screen, seeing this kind of minute detail is impossible just because of how much larger the pixels are compared to HD tv.

This works the same way with the wavelengths of light (just like the size of the pixels on a tv) and how much detail we can see with light. For example: things like molecules and atoms are thousands of times smaller than the wavelengths of visible light, therefor we can't see them even with the most powerful light microscope.

Hope this all helps!

Answer 2

You can only see things which emit or reflect light in the visible spectrum, which is light of a wavelength between 380 and 750 nanometres.

Any light of a wavelength longer or shorter than this will not be seen (hence 'visible spectrum'). This is to do with how our eyes detect light: incoming beams of light will hit specific cells in the retina of the eye; the energy from this light will then trigger a specific biochemical change in in these specialised retinal cells, which will be converted into a neuronal impulse which which travel down the optic nerve letting our brain know what we are seeing. Due to the nature of the chemical reaction the light catalyses, only specific wavelengths of light will activate it - shorter wavelengths would be too energetic, while longer wavelengths wouldn't be energetic enough.

Alternatively, you might be referring to a matter of volume. These cells in the eye require a threshold value of light to 'activate', and transmit the signal to the brain. What this threshold is depends on the individual, and the types of cell involved. Rod cells (which only work in monochrome, and are used for low-light situations) are wired with their neighbours, meaning that a lower level of light (or fewer packets) is (are) required to activate them. Cone cells (which are activated by colour, and are used in well lit situations) require a much higher threshold of light (but then produce a better resolution, not being wired to their neighbours, explaining why things seem blurrier in the dark).