Management Of Natural Resources — Science STD 10 — Question

List the parts of the human eye that control the amount of light entering into it. Explain, how they perform this function?

The chemical substance P is made and secreted by the meristematic tissue at the tip of stem (or shoot) of a plant. The chemical substance P is responsible for a phenomenon Q in plants in which the stem bends towards a source of light. The same chemical substance P has an opposite effect on the root of a plant. It causes the root of a plant to bend away from the source of light in a process called R.

1. What is the chemical substance P?
2. State whether P prefers to remains in the sunlit side of a stem or in shade.
3. What is the effect of substance P on the rate of growth of (i) a root, and (ii) a stem?
4. What is the name of process (i) Q, and (ii) R?
5. What is the general name of chemical substances like P? Name another substance which belongs to this class of chemical substances.

What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:

1. The eye-defect short-sightedness.
2. Correction of short-sightedness by using a lens.

Describe the structure of graphite with the help of a labelled diagram.

Elements forming ionic compounds attain noble gas configuration by either gaining or losing electrons from their outermost shells. Give reason to explain why carbon cannot attain noble gas configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also give reason why carbon compounds are generally poor conductors of electricity.

An element has electronic configuration 2, 8, 7.

1. To which group and period of the long form of Periodic Table does it belong?
2. What is atomic number of this element?
3. Is it metallic or non-metallic and why?
4. Identify the element.
5. Name an element chemically similar to this element.

An object 3cm high is placed at a distance of 8cm from a concave mirror which produces a virtual image 4.5cm high:

1. What is the focal length of the mirror?
2. What is the position of image?
3. Draw a ray-diagram to show the formation of image.

Three incandescent bulbs of 100W each are connected in series in an electric circuit. In another circuit another set of three bulbs of the same wattage are connected in parallel to the same source.

1. Will the bulb in the two circuits glow with the same brightness? Justify your answer.
2. Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

An electric circuit consisting of a 0.5m long nichrome wire XY, an ammeter, a voltmeter, four cells of 1.5V each and a plug key was set up.

1. Draw a diagram of this electric circuit to study the relation between the potential difference maintained between the points ‘X’ and ‘Y’ and the electric current flowing through XY.
2. Following graph was plotted between V and I values:

What would be the values of ratios when the potential difference is 0.8V, 1.2V and 1.6V respectively? What conclusion do you draw from these values?

3. What is the resistance of the wire?

What is methane? Draw its electron dot structure. Name the type of bonds formed in this compound. Why are such compounds:

1. Poor conductors of electricity?
2. Have low melting and boiling points? What happens when this compound burns in oxygen?