Periodic Classification of Elements — Science STD 10 — Question

Explain why the tongue may be considered as both a receptor and an effector organ.

What are the two most common defects of vision (or defects of eye)? How are they corrected?

Define decomposers. Name one decomposer.

What names were given by Mendeleev to the then undiscovered elements.

1. Scandium.
2. Gallium, and
3. Germanium?

A person is unable to see clearly a poster fixed on a distant wall. He however sees it clearly when standing at a
distance of about 2 m from the wall.
a. Draw ray diagram to show the formation of image by his eye lens when he is far away from the wall.
b. List two possible reasons of this defect of vision.
c. Draw ray diagram to show the correction of this defect using appropriate lens.

What is the potential difference between the terminals of a battery if 250 joules of work is required to transfer 20 coulombs of charge from one terminal of battery to the other?

How can you help in reducing the problem of waste disposal? Give any two methods

How does water from the soil reach the leaves of a plant to be used in photosynthesis?

What are the advantages and disadvantages of using nuclear fuel for generating electricity?

The pH values of six solutions A to F are given below:
A = 0, B = 11, C = 6, D = 3, E = 13, F = 8