Our Environment — Science STD 10 — Question

A student uses a lens of focal length -50cm. What is the nature of the lens and its power?

i. By the transfer of electrons, illustrate the formation of bond in magnesium chloride and identify the ions present in this compound.
ii. Ionic compounds are solids. Give reasons.
iii. With the help of a labelled diagram show the experimental set up of action of steam on a metal.

1. Which parts of the eye cause rays of light to converge on the retina?
2. Which part causes the greatest convergence?
3. Which part brings the image into sharp focus on the retina? How does it do this?

An eye has a near point distance of 0.75m. What sort of lens in spectacles would be bneeded to reduce the near point distance to 0.25m? Also calculate the power of lens required. Is this eye long-sighted or short sighted?

What were the limitations of Newlands’ law of octaves?

How is ethene prepared from ethanol? Give the reaction involved in it.

Why does a ray falling normally on a plane mirror, retrace its path?

What is the nature of zinc oxide?

Explain the formation of a chlorine molecule on the basis of electronic theory of valency.

Water is used by the leaves of the plants for photosynthesis but rather than watering the leaves, we water the plant through the soil. How does this water reach the leaves of the plant?