Chickens can see only in bright light. What type of cells is present in their retina?

Which color of light is scattered the most due to the atmosphere?

$A$ person needs a lens of power $-0.5 \text{ D}$ for correcting his distant vision. For correcting his near vision,he needs a lens of power $+1.5 \text{ D}$. What is the focal length of the lens required for correcting his $(i)$ distant vision,$(ii)$ near vision?

Which of the following colors are primary colors?

$A$ person cannot see objects distinctly when placed at a distance less than $50\, cm$.
$(a)$ Identify the defect of vision.
$(b)$ Give two reasons for this defect.
$(c)$ Calculate the power and nature of the lens he should be using to see clearly the object placed at a distance of $25\, cm$ from his eyes.
$(d)$ Draw the ray diagrams for the defective and the corrected eye.

What are the colors obtained by mixing primary colors called?