Human Eye and Colourful World Test - 14

When ray of light enters from a rarer medium (air) into a denser medium(water), it bends towards normal at the point of incidence

The image of an objectseen persists on the retina for 1/16 second even after the removal of theobject. This continuance of sensation of eye for some time is calledpersistence of vision.

The far point is  infinity  for  normal  eye.  It is  the farthest  point  upto which  the  eye can see object clearly.

By convention,

1. The focal length(f) of concave lens is always taken as negative.

2. The object distance(u) from optical centre is always taken as negative. 

As we becomeold,  the power of accommodation of  the eye usually decreases, thenear point gradually  recedes away. This defect is called Presbyopia.Person may suffer from both myopia and hypermetropia.

Correction- Using of Bifocal  lens withappropriate power. Bifocal  lenses consist of both concave andconvex  lens, upper position consist of concave  lens and  lowerportion consist of convex  lens.

Retina works like ascreen or camera film. Retina is full of light and colour sensitive cells.These cells, upon receiving image send electrical signals to the brain, whichprocesses these information to make a mental image of what we see.

Least distance ofdistinct vision for a normal human being is 25cm, however it varies with age.As the person grows old, his ciliary muscle responsible for adjusting the eyelens gets weakened. As a result the power of accommodation reduces and hencethe least distance of distinct vision for old people generally increases.

The pupil of an eyeprovide a variable aperture, whose  size  is controlled by iris

a) When the light isbright: Iris contracts the pupil, so that less light enters the eye.

b) When the  light  is dim:  Iris expand  the pupil,  so that more  light enters  the eye. Pupil open completely, when iris  is  relaxed.

The angle of deviationthrough a triangular prism is defined as the angle between the incident ray andthe emerging ray (angle D).

Colour blindness issaid to occur when a person cannot differentiate between colours although hisvision may otherwise be normal. Causes of colour blindness are genetic and tilldate it has no cure

If you mix red, green,and blue light, you get white light. Red, green, and blue (RGB) are referred to as the primarycolors of light. This is additive color system. As more colors are added, theresult becomes lighter, heading towards white. RGB is used to generatecolor on a computer screen, a TV, and any colored electronic display device.

Electromagneticwaves (or electromagnetic radiation) are waves made of oscillatingmagnetic and electric fields, and include radio waves, microwaves,infrared, visible light, ultraviolet, x-rays and gammarays. Thus, light is just one part of the electromagneticspectrum, the part that our eyes can see.

Frame rate (expressedin frames per second or fps) is the frequency (rate) at which consecutiveimages called frames are displayed in an animated display.The human eye iscapable of differentiating between 10 and 12 still images per second before itstarts just seeing it as motion. That is, at an FPS of 12 or less, our braincan tell that its just a bunch of still images in rapid succession, not aseamless animation. Once the frame rate gets up to around 18 to 26 FPS, themotion effect actually takes effect and our brain is fooled into thinking thatthese individual images are actually a moving scene. The currentindustry standard is 24 FPS.

The refractive indexis a measurement of optical density. A medium with a low optical density, wouldhave also a low refractive index.