Q4 of 56 Page 1

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

The colour of the clear sky during day-time is due to the phenomenon of scattering of light by the molecules of air and other particles in the atmosphere and since they have a size smaller than the wavelength of the visible light, so the particles scatters blue color light rays effectively than that of longer wavelength color.


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2

State one role of ciliary muscles in the human eye.

 3

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

 5

Why do all the elements of the (a) same group have similar properties, (b) same period have different properties?

 6

An element E has following electronic configuration:

K L M


2 8 6


(a) To which group of the periodic table does element E belong?


(b) To which period of the periodic table does element E belong?


(c) State the number of valence electrons present in element E.


(d) State the valency of the element E.