Periodic Classification of Elements — Science STD 10 — Question

1. A ray of white light breaks up into its components while passing through a glass prism. Draw a ray diagram to show the path of rays?
2. Mark the least deviated colour in your diagram?
3. Why do different coloured rays deviate differently in a prism?

The magnification of an image formed by a lens is –1. If the distance between the object and its image is 60cm, what is the distance of the object from the optical centre of the lens? Find the nature and focal length of the lens. If the object is displaced 20cm towards the optical centre of the lens, where would the image be formed and what would be its nature? Draw a ray diagram to justify your answer.

A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.

1. Write the chemical formulae of X and Y.
2. Write a balanced chemical equation, when X is dissolved in water.

Define principal axis, principal focus and focal length of a convex lens.

Explain the meaning of sexually transmitted diseases (STDs). Give two examples of STDs each, caused due to,

1. Bacterial infection.
2. Viral infection. State in brief how the spread of such diseases may be prevented.

Write the number of periods the modern periodic table has. How do the valency and metallic character of elements vary on moving from left to right in a period? How do the valency and atomic size of elements vary down a group?

Comment on the following statements:
(i) Bee sting is treated with baking soda paste whereas wasp sting is treated with dilute vinegar.
(ii) Farmers treat soil with quicklime when tilling.
(iii) Ancient sculptures and marble structures are conserved by treating them with certain chemicals."

What would be observed on adding a 5% alkaline potassium permanganate solution drop by drop to some warm ethanol in a test-tube? Write the name of the compound formed during the chemical reaction. Also write chemical equation of the reaction which takes place.

Two lenses A and B have focal lengths of +20cm and, -10cm, respectively.

1. What is the nature of lens A and lens B?
2. What is the power of lens A and lens B?
3. What is the power of combination if lenses A and B are held close together?

Which uses more energy: a 250W TV set in 1 hour or a 1200W to aster in 10 minutes?