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Q. 5. A wire of resistance 4 is bent to form a closed square. What is the resistance across a diagonal of the square?

Ans. Total resistance of the wire = 4
AB = BC = CD = AD

Resistance across AC is given by R

Q. 6. Redraw the diagram given in your answer book and show the direction of the light ray after refraction from the lens. 1

Ans. When incident ray passes through the focus then refracted ray is parallel to the principal axis.

Q. 7. What is scattering of light? The colour of the sun looks different at different times of the day. Why? 2

Ans.

• Scattering of light means to throw light in various random directions. Light is scattered when it fall on various types of suspended particles in its path.
• The sun and the surrounding sky appear red at sunrise and sunset because at that time most of the blue colour present in sunlight has been scattered out and is away from our line of sight, leaving behind mainly red colour in the direct sunlight beam that reaches our eyes.
• The sun appears white when it is overhead in the sky because at that time the light coming from the sun has to travel a relatively shorter distance through the atmosphere to reach us so only a little of the blue colour of the white light is scattered and most of the blue light remains in it. Since sun has almost all its component colours in the right proportion therefore the sun appears white to us.

Science 2009 Question Papers Class X
Delhi		Outside Delhi		Compartment Delhi		Outside Delhi		Foreign
	Set 1 (PDF)		Set 1 (PDF)		Set 1		Set 1		Set 1 (PDF)
					Set 2		Set 2
					Set 3		Set 3