The twinkling of stars is due to atmospheric:

The figure below shows the refraction of a ray through a prism. Copy the diagram and,ignoring dispersion at the faces $AB$ and $AC$,mark the following angles: $(i)$ The angle of incidence,$(ii)$ the angle of refraction at the face $AB$,$(iii)$ the angle of emergence,and $(iv)$ the angle of deviation.

$(a)$ 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.

Which of the following statements is correct?

Which of the following two colors are complementary colors?

Which lens is used to correct the defect of myopia (nearsightedness)?