Human Eye and Colourful World Test - 16

As the person has the eye defect, myopia, therefore, a concave lens has to be used whose focal length will be, f = -2 m (using sign convention). Thus, Power, (where, f is focal length in metre)

P = 1/f

= 1 − 2

= -0.5 D

The action of ciliary muscles holding the eye lens changes the focal length of eye lens enabling the eye to focus the image of objects at varying distances

The student is suffering from hypermetropia wherein distant images are clear but the nearby images are blurry.

The image of any object seen persists on the retina for 1/16 second, even after the removal of the object. This continuance of sensation of eye for some time is called persistence of vision. The property of persistence of vision is used in cinematography. Iris is responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. Persistence of vision means the image stays on the retina for about 1/16 of a second. This feature is called as persistence of vision.

The atmospheric refraction is the phenomenon that is the reason for the twinkling of stars. The stars twinkle in the night sky because of the effects of our atmosphere. When starlight enters our atmosphere it is affected by winds in the atmosphere and by areas with different temperatures and densities. This causes the light from the star to twinkle when seen from the ground.

Stars twinkle because of turbulence in the atmosphere of the Earth. As the atmosphere churns, the light from the star is refracted in different directions. This causes the star's image to change slightly in brightness and position, hence "twinkle."

The Iris is the colored part of the eye which helps regulates the amount of light entering the eye. When there is bright light, the iris closes the pupil to let in less light. And when there is low light, the iris opens up the pupil to let in more light. Focuses light rays onto the retina.

Human eye and a camera, including: a diaphragm to control the amount of light that gets through to the lens. This is the shutter in a camera, and the pupil, at the center of the iris, in the human eye.

Myopia or Nearsightedness as it is medically termed is a vision condition in which people can see close objects clearly, but objects farther away appear blurred. Myopia occurs if the eyeball is too long or the cornea (the clear front cover of the eye) is too curved.

Most of the red light, which is the least scattered, enters our eyes. Hence, the sun and the sky appear red.