Name the part of the human eye that helps in changing the focal length of the eye lens.

In the dispersion of white light by a prism,which color of light undergoes the minimum deviation?

Which of the following relationships regarding the wavelengths $\lambda$ of different colors of light is correct?

At noon,the sun appears white because:

How is near-sightedness corrected?

$(a)$ Explain the following terms used in relation to defects of vision and corrections provided for them:
$(i)$ Myopia $(ii)$ Astigmatism $(iii)$ Bifocal lenses $(iv)$ Far-sightedness (Hypermetropia).
$(b)$ Describe with a ray diagram how a person with myopia can be helped by spectacles.