Question
An element has Z = 7. What is the valency of the element? Also name the element.
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The given graph (Fig.) shows the displacement versus time relation for a disturbance travelling with velocity of 1500m s–1. Calculate the wavelength of the disturbance.

How are high yielding breeds of poultry advantageous over indigenous breeds?
Distinguish between the following pairs in one or two sentences for each:
Striated and unstriated muscles.
Name the disease caused by mercury pollution of water.
Draw labelled diagrams to represent sound of (a) low pitch, and (b) high pitch, of the same loudness.