What color does the region appear when red,green,and blue light overlap?

Which part of the eye helps in changing the focal length of the eye lens to focus the image of objects lying at varying distances from the eye?

List four common defects of vision that can be corrected with the use of spectacles.

Name the defects of vision of the human eye.

When a beam of white light is passed through a prism,violet colour bends the most and red colour the least.

$A$ myopic person has been using spectacles of power $-1.00\, D$ for clear vision. During old age,he also needs to use separate reading glasses of power $+2.00\, D$. Explain what may have happened to his eyesight?