State one role of ciliary muscles in the human eye.

A 2.4 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 18 cm. The distance of the object from the lens is 12 cm. Find the position, size and nature of the image formed, using the lens formula.

Write the name and formula of the first member of the carbon compounds having functional group-CHO.

Write the name and formula of a molecule made up of three atoms of oxygen.

What is the colour of the clear sky during day-time? Give reason for it.