Electricity — Science STD 10 — Question

How are oxygen and carbon dioxide transported in human beings? How are lungs designed to maximise the area for exchange of gases?

You are provided with two lenses of focal length 20cm and 30cm, respectively. Which lens will you use to obtain more convergent light?

Explain giving one example, how highly reactive metals (which are high up in the reactivity series) are extracted.

Give two uses of concave mirrors. Explain why you would choose concave mirrors for these uses.

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?

1. Draw a diagram to show how a converging lens focusses parallel rays of light?
2. How would you alter the above diagram to show how a converging lens can produce a beam of parallel rays of light.

Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defect.

How does inserting the control rods in the graphite core affect the fission in the reactor? Explain your answer.