P-2 Introduction to Microbiology — Science STD 10 — Question

What are the objectives of disaster management?
(OR)
State any four objectives of disaster management. (March ’19)

A student claims that because of atmospheric refraction, the sun can be seen after it has set, and the day is, therefore, longer than if the earth had no atmosphere.

1. What does the student mean by saying that the sun can be seen after it has set?
2. Do you think that the students conclusion is correct?

When water of mass 70 g and temperature 50 °C is added to water of mass 30 g, the maximum temperature of the mixture is found to be 41 °C. Find the temperature of water of mass 30 g before hot water was added to it.

Write the name of the atom having the smallest size.

Describe the process of preparation of aluminium by the electrolysis of alumina.
(OR)
Draw and label the diagram of electrolysis of alumina and explain the electrolytic reduction of alumina.

Name the elements, group, formulae and physical state belonging to the halogen family.

Describe how petroleum was formed in the earth.

Red colour is used in danger signal.

Explain the terms total internal reflection and critical angle.