Tag: human eye and colourful world

The inability among the elderly to see nearby objects clearly because of the weakening of the ciliary muscles is called presbyopia.

Given that,

Power ${{P} _{1}}=40\,D$

Power ${{P} _{2}}=20\,D$

Total power of the combination

  $ P={{P} _{1}}+{{P} _{2}} $

 $ P=40+20 $

 $ P=60\,D $

Now, focal length of the combination

  $ f=\dfrac{1}{60}\times 100 $

 $ f=\dfrac{5}{3}\,cm $

Now, for minimum converging state of the eye lens object is at infinity

  $ u=-\infty  $

 $ f=\dfrac{5}{3} $

Now, from lens equation

  $ \dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u} $

 $ \dfrac{3}{5}=\dfrac{1}{v}-\dfrac{1}{\infty } $

 $ \dfrac{1}{v}=\dfrac{3}{5} $

 $ v=\dfrac{5}{3}\,cm $

We can not see clearly through fog because the light is scattered by the droplets in the fog. The light is scattered by very small particles, this phenomenon is called Tyndall effect.

The reddish appearance of the sun at sunrise or sunset is due to scattering of light by the molecules of air and other fine particles in the atmosphere.

Sclera protects the eye and gives it shape.

We are able to see objects around us because the light reflected from the object enters our eyes.

The iris gives a distinct colour to the eye is false.
The yellow spot is extremely sensitive to light is false.
The space between lens and cornea is filled with ciliary muscles is true.
The optic nerves enters the eye near the blind spot is false.

Human brain needs some time to process the images. It has the ability to see two distinct images only if the separation between them is one-tenth of a second, otherwise an illusion of continuity is created.