Human Eye and Colourful World — Science STD 10 — Question

A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

An object is placed just outside the principal focus of concave mirror. Draw a ray diagram to show how the image is formed, and describe its size, position and nature.

Draw a ray diagram to show the refraction of light through a glass prism. Mark on it,

1. The incident ray,
2. The emergent ray,
3. The angle of deviation.

Which chemical is injected into the skin of a person:
During the nettle leaf hair sting?
How can the effect of these stings be neutralised?

What is Maxwell’s corkscrew rule? For what purpose is it used?

What are the various conditions necessary for photosynthesis?

The electronic configuration of an element is 2, 8, 4. State its:

1. Group and period in the Modern Periodic Table.
2. Name and write its one physical property.

Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as?

Explain why, the flow of energy in the ecosystem is said to be unidirectional.

What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.