State the names of the hardest material and the softest material.

Give examples of plastic materials

Give examples of elastic material (body).

The material of wire of potentiometer is

Name the factors affecting the resistance of a material.

Name three categories of magnetic material.

Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57V . The threshold frequency of the material is

Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.

Softest tissue is

_______is the hardest natural subtance.